Aside from scones, the king and our love of tea, across the world, people tend to associate London with Big Ben, the Elizabeth Tower is one of the UK’s most famous buildings, standing in the historic Palace of Westminster. It survived two world wars, seen seven different monarchs, and has overseen the transformation of London.
But despite all it’s lived through 30 years ago, the Great Tower was put in a precarious position. And it’s all because of this. The tube station under Westminster was in need of an overhaul. And that meant digging tunnels and expanding below the priceless and not entirely stable foundations of the Palace of Westminster.
working in an incredibly tight space with Big Ben above them and the temps mere meters away. The pressure on this team was through the roof. This is one of the most sensitive construction projects ever undertaken in this city. It’s the fascinating story of Westminster Underground and how it threatens Big Ben. Big Ben or the Elizabeth Tower might just be the most iconic clock tower in the world.
It’s actually just the bell at the top that’s called Big Ben, but for ease, we’re going to use that name to refer to the whole structure for the rest of this video. Completed in 1859, it sits here in the Palace of Westminster, which is nearing a thousand years old. That’s 700 years older than George Washington, 300 years older than Henry VIII, and was probably the last time England enjoyed a rain-free summer.
It’s one of the most historically important areas anywhere in Europe. We shall fight on the beaches. Mr. Speaker, the British people have voted to leave the European Union. We shall fight in the hills. Remember, remember the 5th of November. We shall never surrend
er. But it’s down here where things get really interesting.
This is Westminster Underground Station. Originally constructed by Cut and Cover and opened on Christmas Eve in 1868, but come the 1990s, it was due an upgrade. London’s biggest infrastructure project for over 40 years was underway with the£3.5 billion Jubilee line extension. Westminster Underground was the final station to open on the extension, and there’s a very good reason why it was left till last.
You see, an expansion of this station had been on the cards since the 1960s, but it was, to put it mildly, a little bit tricky. A familiar foe to development in Europe was holding up progress. More than a thousand years of [Music] history. A series of protected buildings lay above the station, including St. Steven’s Club, St.
Steven’s Chambers, and the Palace Chambers. There were objections to knocking them down. That is until Margaret Thatcher came along. Under her guidance, the buildings were flattened. In their place, Port Cullis House was constructed as offices for Parliament designed by Hopkins Architects. It was built as an integrated hole on top of the station with structural elements flowing from the surface down into the new deep level tube platform.
Designing the two things together was an immense technical challenge. Andy Barnett, a principal at Hopkins who worked on this project as a junior architect, says it was incredibly complex. You know, weaving the structure of this heavyweight building above us, which it had to be from a security point of view.
It’s a world heritage site, so it’s heavyweight stone. Getting that to work with this structure beneath it was an amazing technical challenge. Six massive columns take the weight of the downward thrusts from the inner walls of the courtyard. The rest of the load is then supported by a massive concrete core containing escalators and lifts for the deep platforms.
The box is made up of buttressed walls and is supported by solid steel beams measuring 2 ft in diameter to stop the structure from collapsing. The walls, escalators, and ticket barriers follow one of two grids. The diagonal grid of the railway, which cuts across the site at a 45° angle, or the orthogonal grid of the building above.
Then the 30 m deep escalator box to the Jubilee line platforms follows below. But space was far from abundant, and you can see that just by looking up. The ceilings were designed with honeycomb shaped indents coupled with strategically placed lighting to make the absolute most of the limited dimensions on offer. As part of the redevelopment, the existing circle and district tube line needed to be lowered.
That then allowed for the front door of Port Culler’s house to be added at street level while creating space for a ticketing floor to be constructed below and a deep level platform at the bottom for the Jubilee line. We had to lower the district circle line by a foot in itself quite quite a feat of structural engineering.
Once we’ done that, this whole hall was then built below that that hanging as a bridge above us and then we did what was called top down construction and gradually built built this thing downwards. At the time thousands of people were traveling through here every day and it needed to remain active which presented a serious conundrum.
The answer was to suspend 130 m of circle and district line in place while still welcoming trains full of people. Construction happened in phases. So the very first thing they needed to do was build a bridge around the circle and district line and then they had to excavate the box around the rest of the station.
Um but what they ended up doing was essentially taking apart the circle and district line track and just kind of lowering it bit by bit at night during engineering hours. If that’s all sounding like a cup of tea so far, then don’t worry because we’re about to turn up the heat. The real kicker is just across the road.
As I mentioned earlier, Big Ben is old and precious, but has some issues with its foundations. It’s thought that could stem from movement caused by the drying out of the London clay that the tower is built on. You see, when clay gets wet, it swells, and when it dries out, it shrinks. And over time, that causes movements in building foundations.
And as we mentioned, Big Ben has been here for centuries. It wasn’t on the shest of footings back in 1993 and it was thought that it could become a real issue. So caution was crucial. We’re standing at the bottom of a 30 m open box. And when people are moving through this, they’re probably not realizing that we’re actually only a few hundred meters from Big Ben and the Palace of Westminster, one of our nation’s most iconic pieces of architecture, a world heritage site.
Clearly, that’s a pretty delicate structure. In digging this hole, we had to know we weren’t disturbing that in any shape or form. To help maintain the stability of the tower and indeed the palace of Westminster, John Berland, a professor at Imperial College London, was brought on board. Now, on John’s CV, you’ll see that he was also part of a team that worked on stabilizing the Leaning Tower of Pisa.
And last time we checked, that was still standing. So, this guy seems to know his stuff. Before construction had even begun, Big Ben was inclined to lean to the northwest by about 22 cm. The tower’s movement is measured using a weight that hangs on a string called an automated plum line. If the tower tilted, they’d see it in the angle of the string.
As an added measure, an optical plum was installed. It’s generally more accurate and works a bit like this, using light like a laser on a stable base to create a vertical line. daily. They could track any movement to an accuracy of 10 mm. Now, work took place in stages to let the ground settle and to review the impact on the famous old tower before works could then continue.
So, what we needed to do was install steel pipes to make sure that you’re uh keeping big bed from moving. And then we’re injecting grout with the steel pipes to displace any soil that might move. And with that, we kept Big Ben from moving to the point where you would have cracks in its foundation. The positioning of the new Jubilee line tracks was designed with the protection of Big Ben in mind.
They’d run to one side of the massive concrete box, and you’ll notice they’re stacked up. Usually the eastbound and westbound tracks in the London Underground would sit side by side, but here the eastbound tracks sit on top of the westbound line, and it’s to do with vibrations. Trains travel through here constantly during the day, and as you can imagine, over time, that would have a pretty unsettling impact on the surrounding soil.
By stacking the lines, the footprint of the railway was minimized, and the buildings above were spared. But Big Ben wasn’t the only iconic London landmark causing issues for this construction site. Just over the road is the River Temps, 215 mi long and more than 800 ft wide. At this point, it’s not common to dig down and place a 30 m box this close to the river.
And it presented some challenges. During construction of the station, the diaphragm walls began leaking water. One wrong move could have flooded the tube system. Aside from rivers and highly precious buildings, anyone well-versed in London rumors may be wondering whether tunnels had caused any issues. It’s long been thought that a system of underground routes exists underneath Westminster.
Now, while we can’t shed much light on whether MI5 are scuttling about under the city, we do know a tunnel was opened up during construction from the station across Westminster Bridge to the palace. But even if there hadn’t been a system of tunnels to avoid, the challenges faced to redevelop this space were immense.
Damaging Big Ben or flooding the tube would have been no minor accident. But thankfully, the entire station and Port Cullis house above stand as a powerful example of design and engineering mastery. The final result is truly impressive. 25 years later, this is one of the most eye-catching stops on the entire London tube map with its exposed structural elements and dramatic stainless steel escalators against the rough finish of the concrete box.
It’s both bold and brilliant. Westminster underground station is kind of aging like a fine wine. This city could be welcoming further developments to its tube line in the coming years with a possible Baker line extension. Our advice would be to look at what’s been done here and use it as a mark of what can be achieved for the stations of tomorrow.
Westminster Underground is truly impressive and the story of how it came to be will live on and inspire engineers for generations. Don’t forget that we’re raising awareness of construction’s mental health crisis and supporting charities in this space through our Get Construction Talking initiative. There’s a video series on our channel and you can find support or donate over at getconstructiontalking.org.
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