Whilst looking for something totally different on the Discovery TV website, I came across an interesting short video clip about the time when Plessey occupied several miles of tunnel under London and set up a factory inside.

The Central Line extension from Liverpool St was built before the war, but not fitted out for trains until the war finished – priorities being somewhat diverted. After the above ground Plessey factory was bombed by German planes, they decided to move nearly 2,000 people into the newly built tunnels.

The factory specialised in making components for fighter planes and bombers.

The conversion of the Underground was completed in March 1942 at a cost of £500,000 and gave Plessey 300,000 sq.ft. of factory floor.

The 4 and a half minute video clip is on the Discovery Website.

Incidentally, I was looking to see if Discovery Science is going to repeat a program I saw last night about the Jubilee Line extension. While nearly a decade old, the documentary had loads of good footage of tunnels etc. Sadly, I can’t find a repeat date, but did notice that next Sunday (25th Oct), there will be a programme about the building of the Singapore Underground.

Today I finally achieved something I have wanted to do for years, and got to see a rather interesting bit of art into the bargain.

Underneath the Kingway road in Holborn lies the Kingsway Tramway that used to carry electric trams until it was closed down in the 1950s. Since then it has been basically a storage dump for the local council and only on very rare occasions opened to visitors.

Over the next few weeks though, a artist has managed to put a specially designed bit of industrial art inside this closed-off tunnel and is letting people in to have a look.

At the top of the ramp leading down to the subway is a set of locked gates that have stood guard over the entrance, mocking the passers-by who can often be seen peering through the railings and wishing they could stand on the other side.

Today, those gates were flung open and a group of us went down the slope to the dark cavern that hinted of wonders within.

After a brief warning that it would be a VERY bad idea to lean on anything as it is filthy down there, we were taken along the tunnel to the old Holborn Tram Station where we lingered for a short while posing for photos and looking around.

Then down to the art itself.

Basically, two large “knitting machines” that slowly rotate to uncoil ropes which twist to produce a single strand as the machines slowly pull apart along a wooden railway.

The blurb provided said:

Chord is concerned with the human perception of time, as both a linear and cyclical notion. The rope becomes a strong structural metaphor, a clear linear entity made up and formed by a cyclical process. Each point on the rope can be traced back to a certain moment during the cycle and duration becomes interchangeable with length, time with length, time with space, an hour becomes 20cm, a day five meters.

Which is yes, well, quite.

I sort of understand what he is trying to say, but frankly it is not really relevant for me. Either I will like it, or I wont – and explaining it may make me appreciate it more, but it won’t change whether I liked it.

Fortunately, this is something that I liked. Actually, I liked it a lot.

There was something about the very crisp clean industrial machine slowly rotating its kitting yarns as it plied out the rope that really worked for me.

Setting it inside a semi-derelict site added to the experience.

One thing that doesn’t really come across from the photos, or the text I read about it is that the rotating structure moves quite quickly. Although the linear movement is imperceptible, the rotating is reasonably speedy. That seems to make it a much more interesting thing to look at.

Also, unlike some fussy art venues, here is one where people didn’t walk around in hushed awe, but darted around with cameras taking photos with gay abandon. This is art you don’t have to be reverential when granted permission to be within its presence.

The guides who accompanied us down were happy to chat about the art, the tunnel or just gossip.

A hole in the roof was pointed out and they are going to have to work out how to cover it as the unfurling structure moves slowly down the tunnel. Otherwise you are going to get a wet chord.

That hole has allowed a lot of autumn leafs to fall down into the tunnel, and as a bit of art about time, I do like the idea that over this weekend, the spinning structure will “pass through” autumn.

No idea if it was designed that way, or if I am just pretending to be a “wanky art critic” when I noticed that.

Thirty minutes is what you get down in the tunnel and then you are eased back out into the sunlit lands.

I went in unashamedly to see the tunnel. After years of anticipation, it was important for me that the art didn’t spoil the visit, and I am delighted that it added to the experience.

There are a range of events around the installation, including a talk about the art and one about the tunnel.

Various other London bloggers I know have been down there already:

Diamond Geezer, Time Out, Caroline and Londonist.

You can book a free visit via the Measure website, but only have until the 8th November before those gates are once again firmly sealed shut in the face of curious visitors.

Some more photos on my usual Flickr account.

Lurking not too far from where I live is a subterranean marvel that is considered to be one of the most important locations in engineering history. I am referring to the currently closed off East London Line railway – for the tunnel it runs through under the Thames is world’s first (successful) sub-aqueous tunnel.

Not too far from the Rotherhithe tunnel is the Brunel Museum situated within an old pumping station, but conveniently next to the original deep shaft that Marc Brunel (father of more famous Isambard Kingdom Brunel) sunk into the clay soil to get down to the depth where the tunnel would stretch out under the river.

I won’t relate the torturous history of the tunnel itself – as that is amply told elsewhere, for my visit to was not to the tunnel but to the remains of that original shaft.

I arrived at at the museum just as a lot of people were filing out to go to the shaft, so I ahem, joined the crowd. I’ve been in the museum before as they used to run tours of the two key stations, Rotherhithe and Wapping and take a slow train between them.

As part of the refurbishment of the tunnels for the overland railway, the shaft, which has always been empty from surface to deep underground has had a slab of concrete installed and the upper space will be handed over to the museum to clean up and turn into an extension. As the slab was finished off only a few weeks ago – the opportunity here was to see the interior of the shaft before it is cleaned up again.

Getting in for visitors will be down a replica of the original stair case that lined the tunnel when it was open to pedestrians – but our access was through a tiny door that you quite literally had to crawl through and then down some scaffolding to the floor, which is about 3 stories below its roofline (and about 2 stories below ground).

Here lots of photos were taken and a volunteer gave us a brief run through why the shaft is so important in engineering history and some details of its construction.

In essence, they had a huge metal ring, upon which they started building a high wall. As the wall got heavier, it started sinking into the soft soil – aided by workers inside digging out that soil. More bricks added, and the shaft continues to sink into the ground. At one point it got stuck and even adding 50,000 bricks to the top of the shaft wouldn’t unstick the gigantic pipe.

Here there seems to be two variants of the solution – in essence, water leaking into the shaft normally lubricated the sides and one weekend the whole thing dropped down several metres. Whether this was an accidental switching off of the water pumps over a weekend that had a fortuitous outcome, or a deliberate decision seems to vary depending on who is telling the tale.

The shaft finally at its required depth, the tunnel under the river could be cut out. A similar shaft on the north side was also built – although two more shaft, four times wider to allow horses down to the tunnel never got built as some idiot stuck a bridge at Tower Hill and ruined the finances of the tunnel.

Talk over and a climb back out through the tiny exit, and that was it. A short visit, but this subterranean geek was bouncing with delight to have been able to have a look around.

I took a quick look around the museum and picked up a guide book that I would have brought last time I was there, only they couldn’t take cards and I was out of cash on the day. I also had a long chat with one of the staff about the pneumatic railway I am researching and he mentioned something about its precursor at Crystal Palace I wasn’t aware of. More research needed. Yay!

It was a shame we couldn’t go down to the original tunnels – but I have done a slow train tour through there before courtesy of the museum.

A slight rant – they let people into the shaft through a really tiny doorway – and yet other underground structures with significantly easier access points refuse to open up for the public visits due to “health & safety” concerns. That really annoys me as it quite evidently isn’t a problem.

As usual – more photos over at Flickr.

While tunnel affectionados will be familiar with the “Mail Rail” that runs under London, fewer know that it was in fact the second such system, and an earlier tunnel had been built to carry mail from the Post Office’s national sorting centre – by today’s St Pauls tube station – up to Euston Station.

Alas, a financial failure, most of the tunnel still lies under London undisturbed save for the occasional intrusion by modern subteranean mechanical moles.

For me, learning about the tunnel was indirectly responsible for my ongoing, infrequent research of the Waterloo and Whitehall Pneumatic Railway – as part of that, I came across an article in The Windsor Magazine of April 1900. I managed to find a copy, only to find that the bit I wanted was just a single short paragraph – a problem that often aflicts my research, but in buying it I learnt of an attempt to resurect that older mail rail tunnel and return it back into use.

The attempt failed – but the story is facinating, and I transcribe it below for your enjoyment:

(all the images are linked to larger versions on Flickr)

LONDON’S LOST TUNNEL

£175,000 WORTH BURRIED FOR THIRTY YEARS

By Harry Thompson

Is there any other city in the wide world where a cast-iron tunnel, 2¾ miles in length, could lie disused, unknown, lost to the sensory of all but a few scientists, for over thirty years, excepting London? I doubt it. For this commercial hub of the universe spins onward at such a rapid rate, that the doings of yesterday are already shrouded in mist, and those of a decade back buried as deeply as if the dust of centuries, not years, lay upon them.

So it is that, under the hurrying feet of millions, even echoing their tramp through the heart of the great city, for long years has lain this almost imperishable testimony to the enterprise, courage, and, alas ! mismanagement, of certain of its citizens of the “Sixties.” Expert engineers have examined the tunnel and proclaimed it to be composed of the very best metal – “cast-iron such as is not turned out today,” to quote the words of a prominent expert and but little affected by earth, moisture, or disuse, for all its lengthy interment and neglect. Representing as it does the burial of close on £200,000, is it not simply marvelous that no effort until the present has been made to rescue this valuable property from the fungi and huge, whiskered rats, and turn it to some profitable utility? The answer is that the tunnel had been forgotten, simply lost, and the man who “found” it found a gold-mine extending from the G.P.O. at St. Martin’s-le-Grand to Euston Station. Should the sanguine hopes of the discoverer be realized and they are based on the reports of the leading authorities he has “ struck” a payable “lead” that is not likely to be “worked out” until flying machines are as ubiquitous and numerous as hansoms in London streets.

Mr. George Threlfall, a consulting engineer, of 50 Fenchurch Street, “found” the tunnel, and the story of his discovery is one of surmounting almost interminable Alps-of-obstacles, and a period of five years occupied with continual struggle before success crowned his efforts.

The memorable year of 1863 welcomed the abolition of slavery in America, shuddered at the fierce fighting of kin against kin in the Battle of Gettysburg, grieved at the death-beds of three memorable men Thackeray, Stonewall Jackson, and General Sir James Outram-and showered sunshine and good wishes on the marriage of H.R.H. the Prince of Wales.

It saw also the opening of the Pneumatic Dispatch Company’s first section of the tube that later, starting from Eversholt P.O., N.W., passed down Seymour Street under the Euston Station, along Drummond Street, turning into Hampstead Road, and continuing the length of Tottenham Court Road until New Oxford Street was reached, under which it ran, and under Holborn plunging deeply down the Viaduct, passing below Farringdon Street, shooting up into Newgate Street, and finally reaching home in the old G.P.O. buildings on the corner nearer Cheapside. The tube, which measures four feet in height by four and a half in width, was erected to carry the mails and postal parcels between the two terminal points and wayside offices by means of pneumatic pressure.

A lad with a pea-shooter utilizes pneumatic pressure in propelling his stinging pellets by introducing a force of air behind them; in an inverse manner liquids are imbibed thorough a straw by sucking the air out, when the interior liquid, thas relieved from pressure, is forced by the weight of the atmosphere on the outside liquid up through the straw. Both these forms of pneumatic pressure were utilized to drive the loaded cars of the Dispatch Company thorough the tunnel. The car ends fitted the tunnel to within an inch all round. The intervening space was closed so as to be perfectly air-tight by a flange of stout indiarubber, which clung tightly to tile tube’s interior.

The air was sucked out from in front of a train of cars by an ingenious mechanical arrangement. Two discs of wrought-iron, twenty-one feet in diameter, were screwed on to the sides of an iron wheel having sixteen spokes. Between these two discs, and separated from them, stood a third disc of a corresponding size. Thus this cumbers some wheel, complete, contained thirty-two V-shaped cavities. Briefly, it may be said that the revolution of these cavities at a great speed, before huge bell-mouthed pipes, drew by centrifugal force the air out of the tunnel along which the cars, drawn by suction, sped at a rate of thirty-five miler per hour.

The tunnel as it stands to-day is made up of cast-iron sections in nine feet lengths and nearly an inch in thickness. Each section was cast in one piece, and in shape resembles a “D” lying on its back, with a groove in the corners along which the rails are laid. At the stations hermetically sealed spring doors excluded the entrance of air, so that when necessary a vacuum could be produced before the departing cars. The addition of an engine to revolve the hollow wheel I have described completed the whole outfit of a scheme that was to revolutionise the prevailing forms of carriage and general motion. In a Times leader of February 10^th, 1863, I have found the following: “Between the pneumatic dispatch and the subterranean railway the days ought to be fast approaching when the ponderous goods vans which now ply between station and station shall disappear for ever from the streets of London.”

Over thirty-six years have passed, and the railway van is to-day more ponderous, ten times more numerous and a hundred times greater danger to those who use the streets.

And yet we boast of our progress! Nevertheless, the journalists of those days reveled in dreams of pneumatic enthusiasm; and schemes , that doubtless then appeared well controlled and feasible, to-day are known to have been of the wildest and most improbable. Listen to the exultation-cum-wailing of the Seven Days Journey, a propos of the Pneumatic Dispatch Company, under date December 13th 1862: “We are fast making London a marvelous and unequalled city; and if with-all-our improvements and inventions we could only devise some means of rendering the three millions of dwellers in it safe from the murderous attacks of garrotters and , burglars we should have just reason to be proud of our smoke-covered, but unmatched, capital.”

Well, the smoke is still with us in greater volume than of old; but the many-tailed cat has tamed the murderous thief and the Pneumatic Dispatch Company, has been resurrected and is promised a new life with electricity for its vital power.

Yet another reference to “olden times,” and the dead past must give way to the living present. The London Journal, in 1863, printed this piquant paragraph: “Not only have letters and parcels been transmitted, through the tube but we hear also that a lady, whose courage or rashness – we know not which to call it – astonished all spectators, was actually shot the whole length of the tube, crinoline and all, without injury to person or petticoat.” Following on this came a multitude of proposals for pneumatic passenger traction. A trial railway was laid at the Crystal Palace, and proved successful. The Waterloo to Whitehall Pneumatic Railway Company was formed. Great Scotland Yard was fixed upon as a site for one terminal station, and adjoining the Waterloo Station in York Road the other. Excavating and tunneling were commenced. The river was to be crossed in an iron tunnel resting in a dredged channel across its bed. The Illustrated Times of August 17th, 1862 gave a full-sized plate, showing the works in progress, and in accompanying letterpress chimed that, “in its present form, the pneumatic system is simply an adaptation of the process of sailing to railways, the wind being produced by steam-power and confined within the limits of a tube.” Passengers were to have perfect ventilation, no smoke (excepting tobacco), no steam, no jolting, no vibration, no collisions and in fact none of the disadvantages more or less attendant on any railway line in kingdom to-day. Although Messrs. T. Brassey and Co. were the contractors for this ideally perfect railway line I cannot say where it has disappeared to. Evidently it savoured too much of Elysium to be allowed to remain on earthly shores.

Many persons, however, made the journey in the Pneumatic Dispatch Company’s cars. The Evening Standard of April 5th 1868, mentions “Prince Napoleon and his secretary” as being among the passengers, and an illustration on page 623 [image below] shows, the Holborn Station – which was located in close proximity to the present Royal Music Hall – with a departing car passenger-loaded. For this plate I am indebted to Mr. T. E. Gatehouse, responsible editor of the Electrical Review, Fellow of the Royal Society, Edinburgh, a member of the various Institutions of Engineers, Civil Mechanical, and Electrical, besides being a well-known amateur violinist. Mr. Gatehouse entered the service of the Pneumatic Dispatch Company in 1869 – the days of his fallow youth – and scores of times made the journey through the tube lying in the fast- flying cars. “The central station was in High Holborn,” he states, “and contained the whole of the motive power. Here the, cars changed from one set of rails to another and the time taken in completing the whole journey from end to end was nine minutes. It was always an exhilarating journey, the air being fresh and cool even on the hottest of summer days. From Holborn Circus where the tube dives clown a steep declivity under Farringdon Street, the speed was about sixty miles an hour, and in the darkness it felt as if I were sliding down a hill feet foremost.

The impetus of this rush would carry the car up the incline to Newgate Street. To me, who made the trip for the first time, there was something weird and uncanny in being shot through a tube at a high rate of speed, so near the surface of the roadway that the clatter of hoofs and the rumble of vehicles could be distinctly heard, accentuated frequently by the tallow candle or oil lamp being extinguished by the draught. I got so accustomed to the journey that I could tell what corner I was turning. and the streets above precisely at any moment.”

After a period of eight or ten years the Pneumatic Dispatch Company relinquished operations. At intermittent times only had the line been worked; and quietly, without fuss or flurry, as became the collapse of a gigantic scheme, the end came and pneumatic propulsion on a wholesale scale received its death-blow in the minds of experts. The insuperable difficulty lay apparently in the impossibility of rendering the tunnel sufficiently airtight. Leakages of various extents prohibited the creating of a working vacuum, and after the engine-power had been increased until it attained six times its original strength, further efforts were considered useless.

The Company had been an extremely powerful one, with rights and privileges guaranteed to it by special Acts of Parliament. Among the directors were the Marquis Of Chandos, the Hon. W. Napier, Sir Charles J. H. Rich, Bart., Messrs. W. H. Smith, Thomas Brassy, and others. Mr. John Aird was the contractor for the line, of which Messrs. T.W. Rammell and J. Latimer Clarke were the joint engineers.

It was in 1895 that Mr. Thelfall first entered the disused tunnel after struggling and squirming through a heap of debris and lumber in a basement of Euston Station alongside Seymour Street. For many yards from the entrance of this terminal there was a trough to allow of the air propelling a car to escape and thus reduce the impacts on the receiving buffers. An incautious step upon the rotten wooden platform here precipitated the unwary explorer into three feet of stagnant water, but he nevertheless kept his ardour dry, and after several weeks practically completed his inspection of the whole tunnel (excluding the platform below Holborn Viaduct, which he found full of water), and decided that a fair expenditure would put it in working order for the propelling of cars by electricity.

Having discovered the tunnel and realized its effectiveness the still more difficult duty devolved on Mr. Thelfall of finding its owners, the original shareholders, or their heirs, together with the necessary plans and papers. It was indeed strange that the mouth-open tunnel, separated from a busy street by merely an iron railing and a few steps, should remain undiscovered even by these of our community whose misdeeds or intentions force them to hide from the inquisitive glare of X2671’s bull’s-eye lantern and the clink of his handcuffs. In the troublous times of 1883-4 when misguided wretches were attacking with dynamite bombs London’s main thoughfares and buildings, one shudders to think what the knowledge of the tunnel’s existence might have led to on the part of these miscreants. Some dynamite, a line of wire, and a battery spark, and the Nihilist, Anarchist, or Fenian might have sat in safety and ripped a tract of death and desolation throughout the Metropolis. But there are no apparent signs that the tube was ever the hiding-place of any human being. Merely a few, skeletons of rats and, presumably, cats judging by the size – what a Homeric combat of “fighting against odds” do these crumbling bones suggest ! – and here and there umbrella-shaped fungi where the water condensation is greatest.

Stranger almost than the loss of the tunnel was the disappearance of its owners and the papers that would tell who they were. After eighteen months hard search in Government offices and the five parishes through which the tube runs, Mr. Threlfall realised that neither they nor the original contractors had a single plan of the route. It was not until after a wearying system of inquiries half over England and on the Continent that Mrs. Frances Rammell, the widow of the late T. W. Rammell, a famous engineer, was discovered and, through her remarkable energy, the original plans were eventually brought to light.

To realise the commercial value of the tunnel’s discovery and rehabilitation it is necessary to have some slight idea of the extent of mails and parcels passing not only between Euston and the G.P.O., but also between Eversholt P.O., the other local offices en route, and the two main termini. Practically all the heavy post to the north of Great Britain passes through Euston Station, and the heaviest hour of the day sees a total of eleven tons of postal matter leave the G.P.O. for the North-Western Central Station. At present vans carrying from one and a half to two tons each, and taking twenty-four minutes under the most favourable circumstances, make the connecting journey. Heavy traffic, fog, greasy pavements, or other drawbacks to vehicular motion, may double the time occupied. The contract time for the delivery of the mails to the various stations is eight miles an hour, and the enforcement of this rate of speed is one of the G.P.O.’s chief difficulties. For a time motor-cars were tried, but without success. The road to Euston is perhaps the most difficult of all to make progress along, and there is no doubt the tunnel, when fitted will be an enormous convenience to the postal authorities.

When the tunnel is ready, a copper strip will be laid in a trough between the rails, from which an electric-motor drawing a maximum load of seven cars, will pick up the electric current by a roller contact. The current will be supplied by the electric lighting companies and there will be therefore no initial expense for setting up a generating plant. About forty miles an hour, or under two minutes for the journey, will be the highest speed to be attained; and as each car will carry a ton of mails or parcels, seven tones will fly from post-office to station in a twelfth of the time taken by so many horses and vans. There is nothing chimerical or ‘extravagant in Mr. Threlfall’s scheme. The highest experts have endorsed it, and a firm of railway contractors, and also of electrical engineers, now have the preliminary work in hand, on their own stipulations that not a penny is to he paid them should the line-prove a failure, and in consideration of shares and debentures in the new company – the London Dispatch Company – being allotted to them.

Given the success of this electric postman with all restraint of enthusiasm it may be hinted that Paddington, Waterloo, London Bridge, Charring Cross and Victoria are likely to have similar connections to the G.P.O.

Realising the possibility of this and remembering the many journeys made by passengers on the pneumatic railway, it does not seem audacious to imagine high officials or other prominent personages availing themselves daily of this rapid route between the City and the stations, until finally the mails and parcels are relegated once more to the vans and the tunnel devoted wholly to passenger traffic at saloon charges.

A few months ago, I went to a lecture on tunnelling technologies, given by Professor Robert Mair FREng FRS, and specifically on what is known as compensation grouting. Meant to write up about it at the time, but it was not the sort of talk that was easy to write about, as the core of the talk needed the slides to illustrate what was being talked about.

However, the Royal Society – who hosted the talk – put podcasts of their lectures on their website, and today I finally got round to reviewing the details (mainly as the podcast page only works in Microsoft browsers!).

Today, I am going to focus only one aspect of the talk, which was also one of the more famous instances of compensation grouting, and that is the Jubilee Line work around the Clock Tower, more famously known as Big Ben. Timely, as the Clock Tower is 150 years old this week.

As a Jubilee Line tunnel was tunnelled by the tunnel boring machines (TBM), despite the best efforts of the workers, there is always a slight gap between the tunnel wall and the soil outside, leading to some subsidence at ground level. The gap is only a few millimetres, but when amplified around the entire tunnel diameter, that actually adds up to quite a bit of missing soil, and can cause significant problems. Before work starts on any tunnel now, ground surveys and measurements are taken to calculate the subsidence risks and effects on buildings.

In some areas, where the tunnels are likely to cause significant problems, compensation grouting is used.

This is basically steel pipes that are drilled into the ground above where the tunnel is due to be dug – before it arrives – that pump in a slurry type concrete mixture into the ground to “compensate” for the missing soil below.

For the Jubilee Line, this was complicated by the architecture of the location and the fairly shallow foundations of the infamous clock tower. The big risk, which was gleefully latched onto by the news media was that the tower would start to lean sideways towards the tunnel work and may even start to develop cracks or damage. As the TBM worked its way through Westminster, electronic monitors on the tower checked how far it was starting to topple, and then pumped grouting into the soil to basically push the tower back upright again.

The compensation grouting was only carried out at night – as the hole in the ground where they worked was right in the middle of the road, so covered during the day to allow road traffic.

At night the grouting machine was lowered into the hole, shown by the yellow circle.

The pipes drilled reaching under the ground were on average 60 meters in length. The black circles show where the grouting was inserted – and  on average about 150 litres of cement grout was pumped in at each point.

The following slide shows the movement of the tower. They knew the tower could withstand about 15mm of movement, measured at the height of the clock face, before action was needed – and you can see here how the tower started tilting, then a period where the compensation grouting was applied and after tunnelling, the period where the tower more slowly (and safely) settled.

Incidentally, the tower was already leaning before the tunnelling work started – by about 22cm to the North-West, which is said to be just noticeable to the eye.

Without compensation grouting, it is expected that the tower would have tilted by some 10cm at the top – which would have been obviously unacceptable.

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The sides are taken from the podcast on the Royal Society, where you can watch the entire lecture. Note, the slides wont display in either Firefox or Chrome web browsers – so I had to use MSie to watch see them.

I’ll later do a write up about the work at Kings Cross as some aspects of that sound quite interesting, but needs more research work to be carried out.

Incidentally, if you want to climb up the Clock Tower, visits are fairly easy to arrange – a review of the details here.