Deep underneath South Kensington tube station, a huge project is underway to replace all five of the station’s escalators, and all of them at the same time.

To do that though, Piccadilly line trains have had to stop calling at South Kensington station and won’t call there again until next spring. Now, normally when escalators need replacing they don’t have to close part of the station, so why was this necessary at South Kensington?

It helps to understand a little bit about the very complicated history of the station.

A bit of history

The station opened as a sub-surface station, today the Circle/District line platforms.

Later it was decided to add deep level tunnels as well. The deep level tunnels were designed to have four platforms — two for what is today the Piccadilly line, and two for an unbuilt high-speed District line service between South Kensington and Mansion House with just one stop at Embankment.

It was designed so that there would be two eastbound platforms side-by-side, then under them, two westbound platforms, also side-by-side, so that swapping between lines would be easy.

Four lifts would connect the platforms to the surface.

In the end, only the two Piccadilly line platforms were dug, one above the other, and a small part of the high-speed westbound platform which was on the lower level. Two lift shafts, with two lifts in each, plus a staircase connected the Piccadilly line to the surface.

Although the high-speed line was never built, as part of the 3rd platform was dug and completed, it became a useful storage site for the local museums during WW1, and after the war was used for a while as a staff training centre. During WW2 the unused platform was taken over by the London Passenger Transport Board’s engineering and used to monitor bomb impacts that might affect the tube network.

Throughout this, people used the lifts to get down to the two Piccadilly line platforms totally unaware that there was a hidden 3rd platform right next to them. However, in 1970, London Underground announced a £1 million scheme to improve the station, which would also see the four lifts replaced with escalators.

Five escalators in total.

Two escalators lead from the ticket hall to a concourse just below ground, and then three more escalators head down to the lower level, where staircases turn right to the eastbound platform, and down to the westbound platform.

There’s a London Transport poster showing the layout here.

While digging the escalator shafts back in the 1970s, they were able to reuse some of that 3rd platform tunnel for the escalator shaft. So while never used as planned, that high-speed platform is in use today, even if you’d never actually recognise it as such.

All this happened nearly 50 years ago though – and even with regular maintenance, there comes a time when they need replacing.

And that is what is happening at the moment.

In most stations, when escalators need replacing, there is enough space to allow one to be taken out of action while passengers use stairs to go down and the other escalators to go up — but at South Kensington that might have lead to overcrowding at the lower levels during busy periods where there is very limited space, and there’s no way they can take the upper escalators out without diverting people via the already very busy Circle/District line stairs.

It was already looking as if they would have no choice but to close the Piccadilly line platforms, but as we will learn, this project is not a simple swapping out of old for new replacement parts. So in the end they had to close all the escalators entirely. That did however give them the opportunity to what would otherwise be several years of piecemeal work in one big effort.

And what an effort it’s proving to be.

A site visit

Last week there was an opportunity to see the replacement project at a pivotal moment as they have removed the old escalators now, revealing the empty escalator shafts, which are now being prepared to receive the new escalators.

The visit coincided with an unrelated piece of track replacement work at Embankment, so the southern half of the Circle line was closed, as was South Kensington tube station. Going into a normally busy and very familiar station when there’s no one around is an eerie experience. Just people in hi-vis taking advantage of the empty platform for a short break above ground for once.

Taking me around was Adam Thompson, Project Manager Pan TfL Escalator Programme, and down by the supervisor’s office, as we signed in and collected keys, a fox cub wandered out from somewhere onto the now silent railway and watched us at work. Having presumably decided the stack of spare rail tracks it was sitting on was maybe a bit too hot on a sunny day, the fox slipped away and curled up to watch us from the cool shade underneath the railway platform.

Suitably equipped, and heading downstairs into corridors that normally throng with passengers that are now filled with equipment and materials for the escalator project, it feels uncannily like a Hidden London tour. Here though, they’re not abandoned tunnels and London Underground are keen to get them opened again as soon as possible.

So down here under the platforms, is the lower concourse where the two sets of escalators meet, and after months of work removing the old escalators, a huge empty space now stands.

The three escalator shaft down to the Piccadilly line – note where the floor would normally be, at the line where the tiles stop.

Although escalators may not look like they change much in technology terms, in fact, modern escalators are very different from the units installed 50 years ago. The old escalators had to sit directly onto a solid concrete slope with small steps all the way down the slope holding them in place. That’s a lot of concrete.

Most modern escalators are much stronger, so only need to be secured at the top and bottom with a middle support for stability, so considerably less concrete is needed to secure them. That’s brilliant when putting them into a new tube station, but can be a problem when putting them into older sites, such as a 50-year old tube station escalator shaft.

The difference is that modern escalators get their independent strength from having a deeper truss structure underneath the moving steps – so they don’t fit into the same space as older escalators. To make the new escalators fit into the old tunnels, London Underground is having to remove some of the concrete that had held each of the five old escalators in place. But that’s not an easy job.

You can see the steps being cut back from the sides, and removed from the middle. That’s how much concrete needs removing.

So down here in the tunnels, giant rotary saws are slicing several inches of concrete off the slopes for each escalator. Concrete is however a mix that often gets harder as it ages, and reaches peak hardness around 50 years after being cast — which just happens to be right about now, just as they need to break some of it up to make space for new escalators.

What timing!

Some of the huge cutting blades.

It’s not just slicing away at the concrete underneath the escalators that is an issue. The new escalators are a bit longer as well. That’s thanks to an enhancement that reflects the different behaviour of tube passengers rushing to work compared to department store shoppers who are less rushed when using escalators. Also, tube escalators don’t just carry passengers, but have to be stronger than usual to carry engineering equipment at night, which affects their design.

The top and bottom of escalators are flat where you get on and off, and in general, the flat section will be three steps in length. TfL’s standards now call for four steps to be used on the flat sections. It improves safety for passengers, even if it means more work for the engineers installing them.

Twenty-five of the new Otis escalators of the type that will be installed at South Kensington tube station are already in operation at other London Underground stations. They have also been installed on the Elizabeth line.

Therefore, the new escalators aren’t just deeper, but also longer. All for good reasons, but it does mean a lot of old concrete needs to be removed. The top of the escalator shafts is where they are focusing on expanding the space for the new escalators, cutting away the concrete that used to house the old escalator engine rooms.

Standing underneath where the escalators go – looking towards the old engine room

This is another reason why they had to close the Piccadilly line platforms, as cutting the concrete can only be done when there are no passengers around. To have only been able to do that sort of work when the station is closed would have added many more months to the project for each escalator.

Although the new escalators are longer and deeper, they are in fact called “compact” escalators. This sounds odd, but that’s because the motors are now embedded within the main trusses of the escalator rather than being in a separate engine room as the old units used to operate.

So for all the work fitting in a larger escalator structure, they are gaining two large spaces in the storage area where five big motors used to sit.

All that broken up concrete needs to be removed, and a couple of weeks ago one of the passenger tunnels was full of rubble, until a couple of overnight engineering trains arrived. They had just four hours to load all that heavy concrete rubble onto the trains to be removed. Down here, there’s no space for heavy machinery, so all the rubble had to be shifted by hand, and if you’ve ever picked up a piece of heavy concrete, you’ll appreciate how hard the job of loading those engineering trains would have been.

Over the next few weeks, the concrete slopes will complete the process of being lowered to the correct level for the new escalators, and then next month those new escalators will start to arrive. Mostly in kit form to be assembled on-site, although some of the support trusses will come in quite large pre-welded pieces.

A lot of planning has to go into a project like this to ensure the right equipment and people are on site on the correct days, and that in confined working spaces that everything fits.

It would have been ideal to do this during the lockdown, but apart from the difficulty of changing all the plans and having staff work in confined spaces during a pandemic, there was also the issue that TfL was expected to run as many trains as possible to assist keyworkers with social distancing. Closing the platforms was not a realistic option at the time.

Back to the planning, and one early idea to bring the escalator sections into the station was sensibly tested first and a corner where they need to walk around was just a few centimetres too short for the large trusses to fit through. So, plans changed all because of a couple of centimetres of space — but changed before the work had started.

That problem solved, deliveries will start shortly, and assembly of the new escalators will begin. They’ll be working on all five escalators at the same time to bring them back into operation as quickly as possible.

Escalator shaft from the ticket office to the lower concourse.

Once assembled, they have to be run for a period of time to shake out the dust, test them for reliability and grant safety certificates. That done, the escalators and the Piccadilly line platforms will open to the public next spring. Then passengers will arrive, and apart from looking a bit newer, most people would have had no idea of the enormous amount of work that went on underneath to get these new escalators delivered on time.

That’s for next year. At the moment, the construction workers are preparing the site for the new escalator kits to arrive, so time to head back up to the surface and let them get back to work.

Back up in the fresh air on the silent District line, as we signed out and handed over keys, the fox cub looked up at us from under the platform, yawned, and went back to sleep. Deep underground, the concrete cutters were being powered up again and London Underground’s never-ending round of maintenance and repairs resumed.


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Thank you

  1. Terry says:

    Thanks. Really interesting and we’ll written.

  2. Heather says:

    Thank you for this very readable and interesting article.

  3. Progistador says:

    An excellent peice, thank you

  4. Andy B says:

    Really interesting- thank you

  5. Frankie Roberto says:

    Really interesting thank you.

    Did you get any sense of whether it would ever be possible to add step-free access to the Piccadilly line platforms, and if so how?

  6. Melvyn says:

    With work on the Crossrail project coming to an end with delivery of some stations which will have an incline lift beside the escalators I wonder whether this method of renewal might be applied to existing stations especially those with stair free access where the escalators go direct from street to platform level.

    Many stations actually have two escalators and a fixed middle staircase so renewal using this method might allow for two new escalators and an incline lift thus making the station step free without the cost of digging lift shaft . While of escalators vault needs enlarging that would sure still be less costly than a new lift shaft especially as many stations have a design where adding a shaft would be impossible without also building subway tunnels from the lift to platforms.

    I suppose the fall in tourist traffic due to the pandemic will help this work reach completion without causing as much crowding as it would have before the pandemic.

    Given how you say how modern escalators are different from the old design I wonder if closing stations or parts to renew all escalators at once might become a better option in the future

  7. SM says:

    Do you have any more info on “a high-speed District line service between South Kensington and Mansion House with just one stop at Embankment.”?

    sounds very interesting.

  8. Rob Healy says:

    A very interesting read, thanks for sharing the post!

  9. Martin Lee says:

    Very well written article and great to now understand the purpose of the “high speed line” as envisaged. I remember the escalators being installed in 1970 and it was a mammoth task then but a great relief against using the rattling old lifts they replaced. They had lift attendants and took for ever!

  10. Evgenii says:

    Thanks for sharing!
    Even as a civil engineer, it’s interesting to read, language is engaging)

  11. Chris Rogers says:

    Best explanation of escalator work I’ve read. Certainly better than tfl’s… I bet even with an extra step idiots will still fail to step off and so endanger those behind.

  12. Abe says:

    The original plan was only for one eastbound tube platform, not two. Eastbound trains would have shared the same platform (today’s Piccadilly line platform), with the junction just to the east. The space for the junction still exists, and can be seen to the right as trains leave the platform area. The engineers just built an extra-long platform and built a false wall at the end to separate the platform and junction areas. Since the express District Railway was never built, the junction space was never used and is now a storage area.
    Thanks for the great article about the escalator replacement work – very interesting!

    • Taz says:

      Thanks Abe, Explains why part of a fast westbound platform was built to avoid disturbing the lift shaft later, but no need for a fast eastbound platform in the future. The future junction to the west of the westbound platform is also to be seen from passing trains, I believe. The one platform before a junction, but two platforms for merging trains is to be seen at Leytonstone Central line today, and was at Baker Street Bakerloo before the Jubilee line was added there.

  13. Michael Barry says:

    Such an interesting and informative read. Thank you for posting.

  14. Ian Charles says:

    First time I’ve read an explanation for why it can take longer to replace an escalator than it did to install one in the first place. Many thanks for a fascinating article

  15. Nicholas Lewis says:

    Great article and may explains why it takes so long to replace and escalator. Hopefully you can get back there when installation as started to give us an update.
    Never knew about the high speed district line plans either.

  16. SteveP says:

    Great explanation and I finally understand just how complex this work is

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