Engineering places: Thames Tunnel

In the early 1800s, the port of London was considered the world’s largest traffic jam. Cargo ships that travelled thousands of miles would reach Southwark’s Rotherhithe to find that sailing down the Thames would be the slowest, most frustrating part of their journey. This was because goods that were for the southern parts of Britain had to be heaved onto carts and hauled through the docklands. These areas were crammed with pedestrians, particularly across London Bridge.

So, people sought ways to ease the congestion. Building another bridge was not an option as that would deny access for sailing ships to the Pool of London, a part of the Thames just downstream of London Bridge where all the trading ships could unload their cargoes, so engineers turned their attention to creating a tunnel instead.

No engineers had tunnelled under a major river at this time, but the first men to attempt it were gangs of Cornish miners. They were brought to London in 1807 by businessmen, banded together as the Thames Archway Company. The project was led by chief engineer Richard Trevithick.

His team made good progress while tunnelling through London clay, but it was challenging once they got under the Thames. Their pilot tunnel , or driftway, was seamlessly narrow, but sewage-laden water seeped in from the river. In the following year, it was reported that miners hit quicksand then water, which started gushing into the driftway.

The Thames Archway Company called it quits after pumping the tunnel dry, only for it to be flooded again within days.

However, a few years later French émigré Marc Isambard Brunel suggested that the issue could be overcome with a different sort of machine – an invention that could prevent the roof and walls from collapsing, and hold back any quicksand or water at the tunnel face.

In 1818, the eccentric innovator and former naval officer observed the action of a tiny marine borer, the shipworm, whose shell plates allowed it to bore through timber and push sawdust out behind it. Taking inspiration from the shipworm’s burrowing technique, Brunel built a giant iron casing, known as a tunnelling shield, that could be pushed forward through soft ground by means of screw jacks, while miners dug through shutter openings in the face.

The shield consisted of a grid of iron frames that could be pressed against the tunnel face and supported on a set of horizontal wooden planks, called poling boards, that would prevent the face from collapsing. The frames were divided into 36 cells, each three feet (o.9m) wide and around seven feet (2.1m) tall, and arranged one atop another on three levels. The whole machine was 21ft (6.4m)tall, and the working surface was 850 square feet (79m2).

Brunel proposed a tunnel between Rotherhithe and Wapping, and won the backing of private investors in the Thames Tunnel Company. Work on the tunnel using Brunel’s device started in 1825, and while the shield worked well and the miners dug initially through the predicted clay, they began to face some mishaps as they dug deeper. It was reported that water began to drip into the tunnel before the shaft began to pass under the river – a nuisance for workers more than anything while the dry pump was functional. Yet in the summer of 1826, the pump had failed, and the whole shaft was soon flooded.

The project proved even more difficult in the months after this event. Brunel had run short of funds, which resulted in the shaft in the tunnel being poorly drained and ventilated. This then led to miners being poisoned by the polluted river water, and had to endure sudden temperature changes while working – one miner died of disease.

In January 1828, building the tunnel was proved yet again to be a dangerous and deadly job. With the tunnel now well out into the river, water gushed into it, killing six men. Marc’s son Isambard Kingdom Brunel, who was on site, barely escaped alive. The company then suspended construction for seven years due to financial difficulties.

While construction was stalled, critics mocked it as “The Great Bore.” After years of trying to gain financial aid for the project from the government, work on the tunnel restarted in March 1836 with the help of an improved and heavier tunnelling shield to resume the boring.

The tunnel was completed and opened to pedestrians in 1843. Its passageways were filled with souvenir-sellers by day and by the city’s homeless at night. For a penny toll, beggars could bed down under Brunel’s arches in what became known as the Hades Hotel. The tunnel even received an impromptu visit from Queen Victoria and Prince Albert in the summer of that year.

Although the company’s earlier intention was to make the tunnels accessible to horse-drawn carriages, that never happened. Then when the underground railway system was introduced to London in the 1860s, the Thames Tunnel was given a new use. Purchased by the East London Railway Company in 1865, it was found to be in such good condition that it was immediately be pressed into service carrying steam-driven trains – at first along the Brighton line and later from Wapping to New Cross.

Electric trains operated by the Metropolitan Railway began running through the tunnel in 1913, with changes in ownership seeing the line eventually absorbed into the London Underground network. It also continued to be used for goods services as late as 1962. The tunnel closed in 2007 for engineering work under the East London Line extension project, reopening in 2010 as part of the London Overground network that we are familiar with today.

The Thames Tunnel is a touching tribute to both Trevithick and Brunel’s work, and testimony to the difficulties of tunnelling in London in the 19th century. In fact, it remained the only subway line so far to the east until the opening of the Jubilee Line Extension in 1999 because of this. But the construction of the tunnel showed that it was indeed possible to build underwater tunnels, despite the previous scepticism of many engineers. Their great struggle is now of historic importance in one of the UK’s busiest modes of transport today.

Timeline: Thames Tunnel

January 1818: Associate engineer Marc Isambard Brunel presents the idea for the tunnel after obtaining a patent for a circular tunnelling shield of cast iron, designed to protect miners digging by hand behind it.

July 1824: The Thames Tunnel Company is formed.

February 1825: Work begins on the 366m tunnel at the Rotherhithe end in south-east London.

1826: Pump to dry tunnel fails; whole shaft floods to a depth of 12 feet (3.7m).

May 1827: Water breaks into construction works, when the tunnel is 167m long.

November 1827: Isambard Brunel, son of Marc Brunel, organises a grand banquet inside the tunnel.

12 January 1828: Water pours into the incomplete tunnel again. Six men are killed while Isambard, working for his father on-site, is severely injured.

August 1828: Tunnel is bricked up and work is suspended due to financial difficulties.

1833: A loan from the Government allows work on the tunnel to restart.

March 1836: Tunnelling recommences and a new iron shield is built. Shield is moved forward using hydraulic jacks.

1842: An engine house is built next to the Rotherhithe shaft to house machinery for draining the tunnel.

25 March 1843: The tunnel opens to foot traffic, with access via spiral staircases at each end.

26 July 1843: Queen Victoria and Prince Albert visit the tunnel.

September 1865: The Thames Tunnel is sold to the East London Railway Company for £200,000.

7 December 1869: A track is laid and the first steam train runs through it.

31 March 1913: The line is electrified and the Metropolitan Railway begins a service on the East London Line.

29 January 1914: The line is incorporated into the London Underground system. Goods trains also use the tunnel into the 1960s.

1979: The Rotherhithe engine house is restored and now houses the Brunel Museum.

June 1980: Brunel Museum opens to the public.

24 March 1995: Tunnel is Grade II listed in recognition of its architectural importance.

December 2007: The tunnel closes for tracklaying and resignalling works.

March 2010: Tunnel re-opens as part of the London Overground network.