Behind the scenes at Bank tube station’s huge upgrade project

Deep under the streets of central London, huge tunnels have been dug to create a vastly transformed Bank tube station, and the first phase opens in a few weeks time.

This is the Bank station upgrade project.

Away with narrow crowded platforms on the Northern line, and in with wide-open spaces. Away with cramped corridors and stairs to the Central line, and in with a moving walkway. Away with long walks between the street and platforms, and in with escalators and lifts direct from street to platform.

While people using Bank station would have been generally aware that something was going on thanks to all the construction hoardings, as so much of it was hidden from view, few can appreciate just how big the construction site has been. For those not using the station, most would have become aware of the Bank station project earlier this year when part of the Northern line passing through it closed, but that closure was just the final stage of a construction project that, after years of consultations, got underway back in 2016.

In essence, a brand new southbound platform for the Northern line has been dug next to the station and the Northern line closure is to allow that new tunnel to be connected up to the old tunnel. While that is going on, the old southbound platform is having its tracks filled in, and that tunnel is being turned into an expanded northbound platform. In addition, a new entrance being built on Cannon Street will provide escalators and lifts direct to the Northern line, and then down to the DLR — and a new tunnel will link the Northern and Central lines via the moving walkway.

Although construction, which is being carried out by Dragados, has been underway for 6 years, the final stage of completing what they’ve built is being split into three phases.

• Opening the Northern line’s new southbound platform and enlarged northbound platforms – mid May.
• Opening the travolator and escalators to the Central line – late summer.
• Opening the new entrance on Cannon Street with escalators and lifts to the Northern line and DLR platforms – by end of this year.

Last week the Northern line closure reached its midway point, giving a chance to go down into the station and see what’s been built in the spaces hidden from view.

On Cannon Street, a new station entrance box has been built and is now being fitted out internally. Down in the basements under the new entrance, around 100 rooms have been created to provide the back of house space that the station has needed for so long. Elsewhere, they’ve merged the London Underground and DLR control rooms to improve how the station works.

But to get down to the tunnels, it takes 8 flights of stairs down a newly built fire escape to get to the Northern line platforms, and down here, a hive of activity is underway to finish off the work that’s been underway since 2016.

In the past few weeks, what had been the old southbound platform has been totally transformed. The old railway tracks have been removed, and the space where the tracks were has been filled with a new safety smoke extraction system and then covered over. At the moment, it was just possible to see a line in the concrete where the old platform used to meet the tracks, but that will all vanish under the new floor tiles that are waiting to be laid to create a new passenger space.

This space will become an overflow for the existing northbound platform, and to enable that, they’ve been replacing the narrow doorways between the two platforms with wide new entrances. At the far end, you can still see the narrow stairs that people used to use to get onto the platforms — and will once again when the station opens, but sitting next to it, you can still see the old railway tunnel.

As we were here, a chance to do something unusual, to walk down the now disused railway tunnel, where the tracks have been covered in planks and the space is being used for storage by the construction workers. When they’ve gone and the wooden timbers removed, new doors will lock the tunnel although it’ll still be a valuable storage space for maintenance workers. Doubtless one day it’ll be part of the Transport Museum’s Hidden London tours.

There is undeniably something special in being able to stand down here in tunnels that not too many weeks ago were carrying thousands of passengers. The century old cast iron rings contrasting sharply with the pale smooth concrete spaces that have been built nearby to replace them.

What’s replacing the old southbound platform is a huge new space with a new platform that is about three times wider than what people have been used to, and considerably taller, creating a vast almost impossibly large cathedral-sized space deep under the streets.

Something else that’s new to the Northern line, and that’s signs to the lifts. There will soon be direct lifts from the DLR and Northern lines up to street level for the first time at this station. The old meandering lifts will remain, but it’s expected most people will switch to the newer faster direct lifts.

The new southbound platform is also where you can see the new rail tunnel that’s been dug to link up with the old railway. The new tunnel is 488 metres in length, meeting up with the old tunnel some 45 metres to the north of the tube station and 63 metres to the south. The tunnel is very slightly longer than the old, and in theory, an imperceptibly slower journey, but that’s more than offset by avoiding the speed restrictions that were applied to the old tunnel.

But the new journey will be smoother as well.  They’ve also been installing the tracks on a special type of floating bed installation. Effectively, each of the sleeper pads sits on thick shock-absorbing material. Even this deep underground, we’re close to some of the basements of the offices above, so the new track will be much quieter than they’ve had before, and deliver a smoother ride.

When it opens, passengers who keep a close watch out of the windows as they head from Bank towards London Bridge station will also see a wide-open space in the new tunnel. This is where a shaft had been dug down from the nearby Arthur Street as the main access for all the tunnelling equipment to be delivered, and the soil to be removed.

The shaft above has since been filled in, but the underground cavern remains.

All these new tunnels were dug effectively by hand. With no space down here for big tunnel boring machines, to carve out these huge new tunnels they used the sort of equipment you would be familiar with seeing being used to dig up streets. As the clay was dug out, concrete linings were sprayed by hand onto the clay surfaces and then slowly built up until there was a stable solid wall. Waterproof membranes were fitted, and then the final internal concrete linings were sprayed onto the walls. All done by hand.

Now that’s all done, the clean cladding that we will see can finally be added.

When the Northern line reopens in May, the new southbound platform and the enlarged northbound platforms will be completed. But that won’t be the end of the project.

There’s even more to come.

The rationale for this £700 million upgrade of the labyrinthine Bank tube station seems obvious, but it’s the less obvious reasons that justify the work.

Bank tube station before the pandemic was very busy and was expected to reach a point this decade where it would need to be closed at times to control crowds. Even after the pandemic, numbers are reaching a point, especially during the middle of the week where that prediction remains valid.

This is not just a capacity issue, but a safety one. It’s not just that crowds on the narrow platforms are an obvious problem, but if something serious were to happen, evacuating the station is harder due to the way it is laid out.

The main issue is that the Northern line platforms are not just very narrow so there’s a limit on how many people can wait on them, but worse, the stairs lead directly from the platform, so that as people naturally slow down to use the stairs, they bunch up. Crowds building up on platforms is generally something to avoid, so stations have been increasingly built with “sponges”. That’s space away from the platform to absorb the crowds, whether it’s concourses at the bottom of stairs and escalators or corridors that can soak up the crowds and get them away from the platforms.

The main issue with Bank is that having evolved bit by bit over the past century, while it has lots of corridors, they are generally short, narrow, and piecemeal, so they don’t work as capacity sponges.

What is needed is a big sponge.

And that’s part of what has been built — large corridors and large open spaces that have been carved out of London’s soil between the new southbound and old northbound platforms.

Much more space to get away from the enlarged platforms, and while much more pleasant for people, they are also much safer.

The other part of the project though is to improve how people get in and out of the station.

Opening later this summer will be a brand new moving walkway linking the Northern and Central lines. Similar in style to the one at Waterloo station, this new moving walkway will run between the tube lines, and at the Central line end, a brand new bank of three escalators has been added to link the travelator to the Central line.

Those escalators will look normal to people using them, but excavating the space has to be carried out in a very unusual way — bottom up. Normally, shafts are dug from the top down, but to have done that in the space between the Central line platforms would likely have needed the platforms to have been closed for several months. So they dug upwards from underneath the Central line. A delicate and challenging process, that allowed three new escalators to be squeezed into the gap between the platforms without anyone on the Central line ever noticing it was happening.

TfL investigated an option to add a lift as well, but the engineering challenges and costs were so substantial as to rule it out for the time being. If one of the offices at street level is redeveloped in the future, then TfL may be back to take advantage of the space to drop a lift shaft down.

For the moment though, three escalators and two moving walkways will transform the connection between the two lines for the vast majority of people when it opens later this summer.

Then towards the end of this year, the final big upgrade, as the new entrance on Cannon Street opens.

That new entrance will have escalators down to the Northern line, and another bank of escalators down to the DLR.  It’ll also have a lift direct to the Northern line and the DLR. Not only will Bank station gain a new entrance, but it’ll also have a fast and step-free route down into the depths of the station.

Bank station will be transformed with vastly larger spaces and much faster ways in and out of the station. With 40 per cent more space in the station, it’s more spacious for passengers, and with 12 more escalators, wider platforms, corridors and new fire escapes, it’s safer as well.

The upgrade is costing some £700 million, part of which will be recovered from the sale of the building site on Cannon Street for a replacement office block.

This is an upgrade mainly motivated by safety, to prevent the station from needing to be closed if it gets too crowded in the future. But there’s also an economic argument for the upgrade. Partially, a nicer tube service leads to more revenue from fares, and Bank station has long been a station people love to hate and avoid.

But, the biggest economic argument is one that is harder to measure, but very real and one where the bulk of the economic benefit flows to central government, and that’s how the new station will save time on commuting to and from work.

For example, in the peak hours it can take about 8 minutes to get between the Central and Northern lines, but later this year that will shrink to about 2 minutes. That’s about 10-12 minutes every day is saved. Even someone working just three days a week in the office and using that interchange will save about two hours a month from the upgrade to Bank tube station.

Swapping between the DLR and Northern line is expected to drop by an average of 3½ minutes per journey, and later this year the painfully slow crawl out the DLR to the street in the mornings will become considerably faster.

That may mean people get home a little bit earlier, which is nice, but in economic terms, they might get to the office a bit quicker and that may translate into a few emails or phone calls more per month than before. Hard to measure for absolute certainty, but it’s a pretty well accepted principle of how time saved from an efficiency gain leads to more productive outputs elsewhere.

That’s why companies invest in improving efficiencies in the workplace, and why government investments in upgrading infrastructure, whether its roads, railways or these days, internet speeds, also delivers a permanent boost to the economy. A few extra emails a month doesn’t sound like much but magnify it by thousands of people, and now that makes a difference. The economy gets more efficient and grows. That means more jobs for people and more taxes for the government.

So, a railway upgrade being paid for by TfL will in turn increase the size of London’s economy, and ultimately, the UK’s economy.

That’s why this upgrade is not just about making life better for Londoners, but also helps the UK recover from the pandemic, and pumps more money into government coffers to fund the infrastructure upgrades of the future.

But that’s for the future.

At the moment, deep under the City, workmen are adding the cladding panels to cover up the concrete walls, fitting the speakers and lights and adding the new floor tiles. Next month, test trains will start running through the station and staff will be learning where everything is and how to use it.

And in the middle of May, the new Northern line platforms will open to the public. And having been down there to see it all, it’s fair to say that when passengers arrive at Bank station for the first time after it opens… they will gasp.

Some more photos