Today marks the 90th anniversary of the longest tunnel under London opening to the public — following the completion of tube tunnels running down to Morden.

When it opened, 90 years ago today, the tunnels ran for 16.5 miles from Golders Green via Charring Cross (or 15 miles via Bank), making it the longest tunnel in the world at the time.

What was still officially known as the City and South London Railway had been extended southwards to Clapham Common in 1901, but in November 1922 plans were announced to extend it further, all the way down to Sutton.

The plans called for tunnels as far as Morden, then overground, using land that had been reserved for an unbuilt part of the Wimbledon and Sutton railway.

Tunneling is always vastly more expensive than going overground, but unlike the Metroland extension in the north, this was to serve an existing built-up area, so it wasn’t possible to buy up empty fields and then sell off the land for housing. It had to be tunneled, although conveniently, most of the route ran under a major road that ran between Morden and Clapham, reducing some of the cost of running under housing.

The plans for the extension provoked howls of protest from Southern Railway, who were concerned about loss of revenue from the new tube line, and it was a compromise which saw the line terminate at Morden instead, depriving the tube line of Metroland style income from land development.

The extension cost around £5 million to build, and employed some 4,600 men — at a time of high unemployment. Much of the funding for the extension came thanks to a government scheme to boost employment.

Some of the costs were noted in the regional press, as how transport upgrades in London caused investment in the regions.

90,000 tons of iron tunnel rings came from Nottinghamshire and Middlesborough. The 2,900 tons of nuts and bolts came from Wolverhampton. The 2,000 tons of steel railway track came from Leeds and Middlesborough, while fishplates and bolts were supplied from South Wales and Birmingham.

Cement came from Kent and South Essex. Tiles were supplied by Staffordshire and Leeds, while the signaling gear came from Chippenham.

Birmingham factories supplied the new fangled electric signs, and Glasgow the electric cables.

By August 1925, the tunnels were completed, and being fitted out with the tracks and signalling. A curious sight was on occasions seen in the streets above, as modern electric tube trains were hauled through the streets by traction engines down to the new depot being built just to the south of Morden.


The extension is however also noted for the surface stations, all designed by Charles Holden.

These are at:

  • Clapham South (originally to be called Nightingale lane)
  • Balham
  • Tooting Bec (originally to be called Trinity Road)
  • Tooting Broadway
  • Colliers Wood
  • South Wimbledon
  • Morden

These were also some of the first stations to use what we today consider a normal escalator. Before this, most escalators had a sideways shunt to step off, and these new “comb” escalators were seen — rightly — as a radical improvement.

Morden station was also the first to have a dedicated car park. It was just an experiment, and could store 200 cars and had an on-site mechanic to carry out little repairs during the day.

The Morden extension opened on 13 September 1926. On the same day, a rebuilt Kennington station was opened, with four platforms creating the interchange that now exists there.

At the time it was known as the Morden-Edgware Tube, but, a touch over 80 years ago, in August 1937 it adopted its current name, the Northern Line.

A couple of curious asides.

Shortly after the tube opened, it was claimed that during construction, an “army of rats” had terrorised home owners along the extension, driven out of a honeycomb of tunnels under the streets.

One rat catcher, HW Davies claimed that the rats were only emerging above the tube tunnel works, and in one block of flats he had trapped 111 rats in an afternoon.

There were also some new housing developments put up around Morden, and in 1930, they installed half-a-dozen free electric powered boot cleaning machines at Morden station so that people walking through building site mud from the new St Helier estate could get the mud off their shoes before going into the tube trains.

Amusingly though, the mud that so despoiled the shoes of St Helier estate residents, came from the tube tunnels under Picadilly Circus station — it had been carted down from Central London to be used on the estate and help level out the land for building on.


Western Daily Press25th August 1937

Dundee Evening Telegraph20 February 1930

Dundee Evening Telegraph20 September 1926

Western Morning News – 20 November 1922

Dundee Evening Telegraph18 September 1924

Dundee Evening Telegraph10 May 1932

The Times – 22 August 1925

The Times – 3 May 1926



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  1. Kit Green says:

    Tooting Bec station was called Trinity Road until 1950.

  2. Robert says:

    I think you’ve got the distances the wrong way round. It’s longer via Bank.

  3. James Bailey says:

    The line from Morden via bank to Golders Green is 16miles 1,100yards to East Finchley via bank 17 miles 528 yards naturally in tube tunnel

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