Brunel’s Thames Tunnel: The First Tunnel Beneath a Navigable River

London Overground trains run beneath the Thames between Rotherhithe and Wapping every day, and few passengers notice that they are travelling through one of the most stubborn engineering projects of the nineteenth century. The Brunel Thames Tunnel took eighteen years to build, from 1825 to 1843. It flooded repeatedly, killed workers, nearly drowned the young Isambard Kingdom Brunel and stood abandoned for seven years, yet it became the first tunnel known to have been successfully built beneath a navigable river. Our Canals and Railways in the Industrial Revolution tour visits the Brunel Museum at Rotherhithe on Day 21, and this guide explains the problem the tunnel set out to solve, the machine that made it possible and why it still matters.

A river-bottom engineering problem

By the early 1800s the Thames below London Bridge was one of the busiest stretches of water in the world, lined with docks and crowded with sailing ships. Goods and people needed to cross between the docklands on either bank, but a bridge low enough to build would have blocked the tall masts heading for the Pool of London. Going under the river was the obvious answer, and it had already defeated better-funded attempts.

In 1799 Ralph Dodd tried to tunnel from Gravesend to Tilbury and failed. Between 1805 and 1809 the Thames Archway Company brought in Cornish miners, among them Richard Trevithick, to drive a small exploratory tunnel from Rotherhithe. They got about 1,000 feet of a planned 1,200 before the river broke in twice and the scheme was abandoned. Their methods suited hard rock. Beneath the Thames they met soft clay, gravel and waterlogged quicksand, ground that would not stand up long enough to be lined.

How did the Brunel tunnelling shield work?

It turned digging into a controlled, inch-by-inch process in which the ground was never left unsupported. Marc Isambard Brunel, a French-born engineer who had settled in England, patented the tunnelling shield in January 1818. The Brunel Museum notes the often-repeated story that he was inspired by the shipworm, a wood-boring mollusc he had seen tunnelling through ship’s timbers at Chatham Dockyard.

The shield used at Rotherhithe was a great iron framework set against the face of the tunnel. It was made of twelve frames, each weighing more than seven tons, and each frame was divided into three storeys, giving 36 cells. One man worked in each cell. The face in front of him was held back by a stack of wooden boards. He removed one board, dug out a few inches of ground behind it, and replaced the board against the new face, working down the stack one board at a time. When a whole frame had been dug forward, screw jacks pushed it ahead against the brickwork already built behind it, and bricklayers immediately lined the newly opened space.

Progress was painfully slow, often between one and eight feet a week, but the method meant soft ground could be tunnelled at all. The finished structure is about 1,300 feet long, 35 feet wide and 20 feet high, built as two parallel brick-lined passages joined by a series of cross arches, and lies about 75 feet below the surface of the river at high tide.

Sinking the shaft at Rotherhithe

Before the shield could start, the Brunels needed a way down. Work began in February 1825 with an unusual solution. On the Rotherhithe bank they built a brick cylinder 50 feet across on top of an iron ring, with a steam engine on top to pump out water, and then dug away the ground beneath it so that the whole structure sank under its own weight. Partway down it stuck, and 50,000 extra bricks were piled on to drive it the rest of the way. By November 1825 the shaft was in place and tunnelling could begin. Later shafts were built tapering to avoid the same problem.

That shaft survives. Its upper part is now the Brunel Museum’s Tunnel Shaft, a ten-metre-high brick chamber that was opened to visitors in 2016 for the first time in more than 150 years.

Soft ground, flooding and persistence

The river was never far away. At times only a few feet of loose gravel separated the shield from the riverbed, and conditions at the face were grim. Foul water from the polluted river seeped in, methane and hydrogen sulphide built up, fires broke out, and men fainted at the shield or suffered dizziness, chest pains and failing eyesight. Isambard Kingdom Brunel, Marc’s son, became resident engineer in April 1826 at the age of twenty, and much of the daily responsibility fell on him.

On 18 May 1827, with 549 feet complete, the river burst in. Isambard went down in a diving bell to inspect the hole in the riverbed and had it plugged with bags of clay. Once the tunnel had been pumped out, he held a banquet inside it, with a band playing, partly to reassure investors. The Brunel Museum still calls it the first underwater concert party.

The second flood, on 12 January 1828, was worse. Six men died. Isambard was nearly drowned himself and was rescued by a contractor named Beamish. With money exhausted, the tunnel was bricked up behind the shield and left for seven years.

Marc Brunel never gave up on it. In December 1834 he secured enough money to restart, including a Treasury loan of £247,000. The old shield was removed from August 1835 and a new, heavier one was in place by March 1836. There were further floods in 1837, 1838 and 1840, but the tunnel was now being driven with more experience and better equipment. Excavation was completed in November 1841, the year Queen Victoria knighted Marc Brunel for the work.

From underground spectacle to transport infrastructure

The Thames Tunnel opened to the public on 25 March 1843. It had cost about £454,000 to build and another £180,000 to fit out, far beyond the original estimates, and the ramps needed to bring horse-drawn vehicles down to it were never built. Instead it opened to pedestrians, who paid a penny to walk through.

Londoners and visitors came in huge numbers. About 50,000 people are said to have walked through on the first day, and more than a million within fifteen weeks. Stalls set into the arches sold souvenirs and refreshments, and fairs were held underground. As a novelty it was a triumph; as a business it struggled, because few people needed to cross the river on foot at that point.

The railway gave it a lasting purpose. The East London Railway Company bought the tunnel in 1865 for £800,000, and the first train ran through on 7 December 1869. Wapping station opened in 1884 in the disused northern shaft. The line later became part of the London Underground, and since 27 April 2010 the tunnel has carried London Overground trains. It was listed at Grade II* in 1995 and was named an International Historic Civil Engineering Landmark by the American Society of Civil Engineers and the Institution of Civil Engineers in 1991.

Why does the Thames Tunnel matter to engineers today?

Because the shield worked, and its principle outlived the tunnel. The idea of supporting soft ground at the face with a movable frame and lining the tunnel immediately behind it was refined by later engineers and became the basis of shield tunnelling. Modern tunnel boring machines, which drive and line tunnels in a single continuous operation, follow the same logic Marc Brunel patented in 1818. The Thames Tunnel proved that a navigable river could be crossed from below without stopping the ships above it.

What will you see at the Brunel Museum?

The Brunel Museum occupies the engine house the Brunels built at Rotherhithe beside the tunnel shaft, and its exhibition tells the story of the tunnel and the Brunel engineering family. The museum also gives access to the Tunnel Shaft itself. Reaching the floor of the shaft means three flights of stairs with handrails; visitors who prefer to avoid them can look into the space from a viewing platform at the top, and the museum suggests contacting it in advance about specific access needs. The tour is rated Level 2 (Moderate), with three to five hours of activity on most days, roughly equivalent to walking up to 8 kilometres, sometimes on uneven ground.

The tunnel in the tour’s Brunel sequence

The Thames Tunnel comes at the end of a short run of Brunel days that show father and son at work in very different settings. Day 20 is spent in Bristol, with a guided tour of the city, a stop at Isambard’s Clifton Suspension Bridge across the Avon Gorge and a visit to the SS Great Britain, his iron steamship launched in 1843, the same year the Thames Tunnel opened. On Day 21 the group travels to London by way of the STEAM museum in Swindon, the Great Western Railway’s former works town, before visiting the Brunel Museum at Rotherhithe.

Seen at the end of the route, the tunnel completes a story the tour has followed since its first days. At Ironbridge Gorge the group sees how cast iron first spanned a river, and on Day 15 in Darlington the Stockton and Darlington Railway shows steam locomotives beginning to haul coal and passengers in 1825, the same year the Brunels started digging at Rotherhithe. The Thames Tunnel solved a different kind of crossing, and it ended up serving the railways that grew out of those beginnings.

Our guide to Britain’s canals, railways and industrial heritage shows how each of these sites fits into the full journey from Manchester through Wales, Scotland and the north-east to Bristol and London. For dates, inclusions and the complete itinerary, see the Canals and Railways in the Industrial Revolution tour, which travels in small groups of 6 to 14 with an Odyssey Program Leader.