Right by the entrance to the Tower of London, few people give a second thought to a little, round, brick building with Tower Subway written around the top.

The structure only dates from the 1920s, but the writing informs you that Tower Subway was constructed in 1868.

But it still presents an intriguing question…

What was the Tower Subway?

Before Tower Bridge was finished in 1894, London Bridge was the only river crossing in this part of the city and was heavily congested.

A plan was hatched to dig an underground tunnel for trams between Tower Hill and (the brilliantly-named) Pickle Herring Stairs, just off Tooley Street.

Image from Reynolds’ Shilling Map, 1895. Wikimedia Commons, Public Domain

It wasn’t the first tunnel to be constructed under the Thames (that honour goes to Brunel’s Thames Tunnel between Wapping and Rotherhithe from 1825-1843). However, the excavation was an important step in engineering.

It was first time that Sir James Greathead’s tunnelling shield was used.

Statue of James Henry Greathead in Bank Junction. Erected in 1994 and designed by James Butler. Look closely at the base and you can see it’s actually a cleverly disguised air vent for Bank Station below!

A tunnelling shield was the principle of forming a protective structure while digging through soft earth. It was first implemented by Marc Brunel, but it was Greathead – under engineer Peter Barlow – who improved the technique by using a circular shape.

In fact, it’s James Greathead who we can thank for the underground’s nickname; The ‘Tube’.

WHAT HAPPENED TO TOWER SUBWAY?

Tower Subway opened for passengers in 1870, only taking a year to complete, however speed didn’t guarantee success.

The Tower Subway was similar to underground tube lines today, although with cables pulling carriages along rather than electricity. Each carriage could hold 12 people.

Image from Wikimedia Commons, Public Domain c.1870

Originally there were lifts that brought passengers back up to ground level and on the face of it, it seems brilliant, the whole process taking under 2 minutes to get across the river.

However, the lifts were plagued by breakdowns and there was one horrific accident where a poor man named Thomas had his head crushed in the lift shaft.

Less than a year after it opened it had become a fully pedestrianised tunnel, with people paying a small toll to walk under the Thames. At its peak, one million people per year walked through it, pretty amazing numbers considering an average of 1.2 million use Greenwich Foot Tunnel annually today.

But with the arrival of the (free) Tower Bridge, that all changed. It closed in 1897 and was bought by the London Hydraulic Power Company as a convenient place for its mains under the Thames. Today it still houses water mains and telecommunications cables.

What Can you See today?

As you may have guessed by its size, this wasn’t the original public entrance to Tower Subway, but rather this is a 1920s replacement which gives maintenance access to the shaft below. But there is more. After all, a tunnel needs to have a Southern Entrance right?

The warehouses along Tooley Street have now pretty much all gone, swallowed by the More London development. But tucked out of sight you can find the site of the Southern Entrance;

Far more mundane and modern-looking, it can easily be missed. But, even if it’s not as eye-catching, it’s still a sneaky clue to London’s history!

More London Inspiration