The Thames Tunnel

The Thames Tunnel

When it first opened in 1843 the Thames Tunnel was described as the Eighth Wonder of the World. People came from far and wide to see the first tunnel under a river anywhere in the world.

On the opening day, fifty thousand people descended the staircase and paid a penny to walk through the tunnel. By the end of the first three months there were a million people, or half the population of London. In its day, this was the most successful visitor attraction in the world.

In the age of sail and horse-drawn coaches, people came from all over the world and bought souvenirs and listened to the entertainment in the cross-tunnel arches.

The idea, of course, was not entertainment but to move cargo and turn a profit. So what happened?

The Need For A Tunnel

The proposal to build the tunnel had to take account of the sailing ships on the River Thames. The Port of London was the busiest in the world and the hub of trade across the British Empire. Any bridge built would have to allow ships with masts over 100 feet tall to sail under them, and the technology of Tower Bridge’s lifting bascules was not available to these early engineers.

A horse could not pull a loaded cart up a very steep hill, and to get 100 feet up into the air at a gentle gradient the approach ramps would have to be so long as to be impractical.

So it was that Marc Brunel proposed a crossing under the Thames using a tunnelling shield, a piece of equipment that would support the tunnel’s walls and roof as it was dug out, giving the bricklayers time to line the tunnel and create a solid structure. Horses pulling their loaded carts would descend on giant spiral ramps in new shafts 200 feet wide.


Work started in 1825 but even with the tunnelling shield it was going to be dangerous work building a tunnel through the soft soil found under the River Thames.

The shield was rectangular and had 12 digging positions across its width and three digging positions on top of each other so allowing 36 miners to work simultaneously. in front of each miner there was a series of horizontal boards. The miner would unscrew the top one to expose the earth and would then dig horizontally away from him two inches of earth. He would then replace the board screwing it tight into the void he had created. He would then unscrew the next board down and do the same. Once he had got to the bottom board he would start from the top again. The second time he finished at the bottom board his whole digging position would be jacked forward using screw jacks and the process would be started again. So the Thames Tunnel was dug a few inches at a time for 1,200 feet across the River Thames.

Working in the tunnel the air quality was appalling with the workers frequently being dragged senseless up to the surface to recover in the fresh air. Conditions were also very damp with water constantly coming in from the River Thames above. But worse, this was the River Thames before Sir Joseph Bazalgette and his sewer system for London. The River Thames was no better than a sewer, and the sewage entering the tunnel gave off methane gas which was frequently set alight by the candles that provided a dim light for the workers – there were no miner’s safety lamps in the Thames Tunnel.

On several occasions the miners tunnelled too close to the river bed causing the water to flood into the tunnel and the miners to run for their lives. On one of these occasions Isambard Kingdom Brunel was almost killed. The solution to restarting work was to drop thousands of sandbags filled with clay and chisels sticking out of them so they would hold together. Once the water stopped entering the tunnel it would be pumped dry, the debris cleared away and work would start again.


In 1843 the tunnel finally opened, but only to pedestrians and not the horses and carts carrying cargo that had been the sole reason for creating it. The tunnel had taken so long to build there was simply no money to build the two large shafts with spiral ramps that the horses and carts would use to descend and ascend.

However with it being dubbed the 8th Wonder of the World the crowds flocked to it creating a brief profitability. Inevitably this was not to last as its novelty passed and the Thames Tunnel Company ran out of ideas to promote it with.


A railway company took over the tunnel in 1865 with the intention of digging new tunnels to link up from the North and South to link the Thames Tunnel to the national railway network. Four years later, in 1869, trains started to run through the tunnel meant  for horses and carts. For the first time the tunnel was doing what it was intended to do – carrying freight across the river.

In 1869 electric trains had not yet appeared on the national network, so the trains running through the tunnel were hauled by steam engines. Entering the tunnel the trains would go downhill towards the low point at mid-river before starting the hard climb back up to the surface. The harder a steam engine works the more smoke it produces. In railway tunnels on land there are frequent shafts to allow the smoke to escape to the surface. No ventilation shafts could be built in the river so The Thames Tunnel was full of smoke making life very unpleasant for the steam engine drivers and firemen.

London Overground

2010 saw the re-opening of the Thames Tunnel as part of the London Overground. What was once the stub East london Line has now metamorphosised into the London Overground creating new routes linking destinations north and south of the river. Eventually this will become part of an orbital railway – an outer Circle Line.

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