A Look Inside The Bascule Chamber Of Tower Bridge

I recently went on a preview Behind the Scenes tour of Tower Bridge. This included going across the famous glass walkways at the top but also down into the cavernous bascule chamber below the South tower. 

A Quick History Of The Bridge

In the 1800s, the population of London skyrocketed from roughly 1 million in 1800 to around 6 million in 1900. 

The majority of that growth had been in the East End and the most Easterly bridge was London Bridge. A new bridge for London was therefore required. 

A competition was held to design it, the condition being that it had to allow shipping to be able to pass through it into the upper pool of London. 

Various designs were proposed such as this one by F J Palmer.

The Winning Design

In October 1884 the winning design by Charles Barry in collaboration with Sir John Wolfe Barry was selected.

It is a bascule bridge. ‘Bascule’ roughly translates from French as ‘seesaw’ as the arms or bascules of the bridge seesaw or pivot on an axis to allow them to be lifted and boats to pass through. 

To give you an idea of how much quieter the river is today, in the 1890s the bridge was being lifted around 6000 times a year, today it is around 800 a year and that is apparently predominantly for booze cruises. 

Each arm weighs 1200 tonnes and has a 400 tonne counterweight on the end that helps it to descend down into the huge bascule chambers below each tower. 

Behind The Scenes

On the Behind the Scenes tour you climb (or get the lift) up the North tower where there are various interesting things to see. 

I particularly enjoyed seeing the weighted diving suit.

This is what divers wore to dig the silt out of the caissons (essentially a box that gets sunk into the riverbed for the towers then to be built on) before the towers were then constructed. 

The divers would be dropped into the river, the weighted boots, helmet and weight around their neck would sink them to the bottom where they would then work a 9 hour day underwater excavating the silt. 

Another fun fact we were told is that you can hire the bridge for weddings. They have to however take place in the North tower as that one sits in in the Borough of Tower Hamlets who have granted the bridge a license whereas the South tower is in the Borough of Southwark, whose council have not allowed it.

The Walkways

You then walk over the walkways between the towers with their famous glass floors.

The walkways were originally intended for pedestrians to walk over when the bridge was up but it often took longer to walk up and over than just wait for the bridge to open so they were shut for many years.

Control Cabins and Engine Rooms

As we were on the Behind the Scenes tour we then went into one of the old control cabins, guided by one of the bridge’s engineers.

These were used up until the 1970s and you can see all the original levers.

These had to be pulled in a specific order to open the bridge. This is all done via a computer today of course. 

We then went down into the engine room. This is one of the modern engines that operates the bridge today.

You can see the old Victorian one just next to it.

Tower Bridge is operated by hydraulics, originally using coal generated steam to power the pumping engines. Today it is driven by oil and electricity. 

The Bascule Chamber

It is about 115 steps down below water level into the chamber. 

You pass by the accumulator. These essentially act like batteries, storing the energy generated by keeping the water under high pressure.

You then enter the bascule chamber itself.

It really is pretty atmospheric. You feel as if you have slightly descended down into another world, into the belly of the beast. It is a bit cold, damp and you can hear the traffic rumbling overhead.

If there was a bridge lift, the counterweight would help pull the bascule or arm of the bridge down into this chamber to lift it. 

They actually even hold concerts down here very occasionally which must be very bizarre and atmospheric. 

The tour was really brilliant and it was fascinating to see the workings of the bridge. I also made a short video of my visit that you can watch that here. 

You can book tickets here.

I have written a blog post previously on the bridge, with 12 fun facts, that you can read here. 

Thank you for reading, more of London’s history below…