Thames Tunnel

• 1. Introduction

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  The Thames Tunnel runs beneath the River Thames in London, connecting Rotherhithe on the south bank to Wapping on the north. At 1,300 feet long, 35 feet wide, and 20 feet high, it sits 75 feet below the river surface at high tide. What makes it remarkable is not its size but its precedent: it was the first tunnel ever successfully built beneath a navigable river.

  Before it existed, engineers who tried to cross the Thames underground failed. A project involving Cornish miners was abandoned after floods destroyed the work. The received wisdom among the profession was stark: an underground tunnel beneath the river was simply impracticable. One Anglo-French engineer, Marc Brunel, refused to accept that verdict.

  What followed was nearly two decades of floods, deaths, financial collapse, and a tunnel that became something few civil engineering projects ever become: a place where you could buy a souvenir, listen to a pipe organ, and have your fortune told by an Egyptian necromancer.

• 2. Failed Attempts

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  Ralph Dodd tried in 1799 to bore a tunnel between Gravesend and Tilbury, and he failed. Between 1805 and 1809, a crew of Cornish miners, including Richard Trevithick, attempted a crossing further upriver between Rotherhithe and Wapping. They got further than Dodd but still came up short.

  The Cornish miners were expert at cutting through hard rock. Soft clay and quicksand were another matter entirely. Their tunnel, called the Thames Archway, flooded twice before the work was abandoned. By that point they had dug 1,000 feet of a planned 1,200. The pilot tunnel, a narrow driftway measuring five feet across, had been intended only as a drain for a larger passenger tunnel above it. When the project collapsed, the engineering profession drew what seemed like a logical conclusion: crossing beneath the Thames underground was not possible.

  Marc Brunel saw the problem differently. He understood that the failures were not evidence against tunnelling under rivers. They were evidence that the existing methods were wrong. He spent the years after the Thames Archway failure developing a new approach, and in January 1818 he patented what he called a tunnelling shield.

• 3. The Shield and the Shaft

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  Brunel's tunnelling shield was assembled at Henry Maudslay's works in Lambeth, then lowered into the ground at Rotherhithe. The Illustrated London News described it as twelve great frames, arranged like books on a shelf, each divided into three stories. That gave 36 individual cells, one miner per cell. Each miner removed a single board, dug into the earth behind it, then pushed the board forward against the new face. The whole frame then advanced on screw jacks, pressing against the finished brickwork behind it. One end dug; the other end built.

  Each of the twelve frames weighed over seven long tons. The shield's purpose was to hold the surrounding ground in place as the tunnel was cut, reducing the risk of collapse.

  Before the shield could be used, a massive shaft had to be sunk at Rotherhithe, 150 feet from the riverbank. Workers built an iron ring 50 feet in diameter at ground level, topped it with a brick wall 40 feet high and more than three feet thick, then placed a steam engine on top to drive the pumps. The entire structure weighed an estimated 1,000 long tons. By removing the soil under the ring's lower edge, they let it sink into the ground under its own weight, like a pastry cutter pressing through dough.

  The shaft got stuck partway down. The parallel sides created too much friction against the surrounding earth. The engineers added 50,000 bricks as temporary weights to force it deeper. Years later, when the companion shaft at Wapping was built, the engineers tapered it so the bottom was slightly wider than the top. It never got stuck. By November 1825 the Rotherhithe shaft was in place and the tunnelling could begin in earnest.

• 4. Floods and Near-Death

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  Work inside the tunnel was slow, progressing at roughly a foot per day on average. The ground above was the bed of the Thames, and the water did not stay above it. Sewage-laden river water seeped through continuously, releasing methane that ignited against the miners' oil lamps. Marc Brunel and many of his workers fell ill from the conditions. When the resident engineer John Armstrong collapsed from illness in April 1826, Marc's son Isambard Kingdom Brunel stepped in at the age of 20.

  To generate income while the work dragged on, the company sold tickets to sightseers who wanted to watch the shield in operation. They charged a shilling a visit. Between 600 and 800 people took them up on it every day.

  On the 18th of May 1827, after 549 feet had been excavated, the roof gave way and the tunnel flooded without warning. Isambard lowered a diving bell from a boat on the river to inspect the breach from above, packing bags of clay into the hole. After the water was pumped out, he hosted a banquet inside the tunnel to reassure investors and the public that construction would continue.

  The second flood, on the 12th of January 1828, was far worse. Six men died. The event came just four days after a visit by Don Miguel, who would soon become Regent of Portugal. Isambard was nearly among the dead. The men rushed to the main stairwell, but the emergency exit was known to be locked. Isambard went the other way, toward the locked door. A contractor named Beamish heard him there and broke it down. Isambard was pulled out unconscious and revived. He was sent to recuperate at Brislington, near Bristol, and it was there that he first heard about the competition to design what would become the Clifton Suspension Bridge.

• 5. Completion and Cost

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  After the second flood, construction halted entirely. The tunnel sat unfinished for years. Marc Brunel eventually raised enough funds to resume, including a Treasury loan of £247,000 secured in December 1834. Work restarted in August 1835 when the old rusted shield was dismantled and removed. A new, heavier version was assembled and boring resumed in March 1836.

  Four more floods struck between August 1837 and April 1840, along with fires and leaks of methane and hydrogen sulphide. The remaining length of the tunnel was not completed until November 1841, five and a half years after the restart. The extended delays made the tunnel a target for satirists and comedians in the London press.

  The fitting-out of the tunnel with lighting, roadways, and spiral staircases continued through 1841 and into 1842. An engine house on the Rotherhithe side was also built to house the machinery that kept it drained. The Thames Tunnel opened to the public on the 25th of March 1843.

  The final cost was staggering. Digging the tunnel alone had cost £454,000. Fitting it out cost another £180,000. Both figures far exceeded the original estimates. Proposals to extend the entrances so that horse-drawn carriages could actually use it, as originally intended, were abandoned as too expensive. The world's first successful underwater tunnel became, from its opening day, a pedestrian walkway.

• 6. The Underground Marketplace

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  About two million people visited the Thames Tunnel each year, each paying a penny to pass through. They did not find a spare, utilitarian passage. The American traveller William Allen Drew, who saw it in 1851, called it the eighth wonder of the world and observed that no one went to London without visiting the tunnel.

  What they found inside was closer to a bazaar than a transport artery. The entrance at Wapping was an octagonal marble building whose rotunda measured fifty feet across, with a mosaic floor in blue and white. Stalls sold papers, books, and confectionery. A pipe organ played on the first landing as visitors descended the marble stairs.

  The tunnel itself consisted of two arched roadways, each fourteen feet wide and twenty-two feet high, separated by a partition wall cut through with transverse arches. Those arches were fitted as fancy and toy shops, with polished marble counters, tapestry, gilded shelves, and mirrors. Drew noted that the women tending those stalls let no gentleman pass without offering him a souvenir. Most items were labelled "Bought in the Thames Tunnel" or "a present from the Thames Tunnel".

  Not everyone was charmed. Nathaniel Hawthorne visited a few years after Drew and wrote in 1855 that the tunnel was "an entire failure" as far as any practical use was concerned. He described a gloom lit only by gas jets at regular intervals, women selling what he called multifarious trumpery from alcoves, and people who appeared to spend their lives underground. Other visitors described the tunnel as the haunt of prostitutes and thieves who preyed on those who lingered in the arches.

• 7. The Railway Conversion

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  In September 1865, the East London Railway Company purchased the tunnel for £800,000. The company was a consortium of six mainline railways that wanted a rail link between Wapping and the South London line. The tunnel's dimensions, built to accommodate horse-drawn carriages, happened to provide an adequate loading gauge for trains.

  The line's engineer was Sir John Hawkshaw, who was also known for completing Isambard Brunel's abandoned Clifton Suspension Bridge in Bristol, finishing that project in 1864 with W. H. Barlow. The first train ran through the Thames Tunnel on the 7th of December 1869. The disused northern shaft was repurposed in 1884 as Wapping station.

  The East London Railway was eventually absorbed into London Underground as the East London line. Goods services continued running through the tunnel as late as 1962. Through all those decades, the Thames Tunnel held the distinction of being the oldest piece of underground infrastructure on the entire Tube network.

  A planned connection to the Jubilee Line extension at Canada Water station required temporarily closing the East London Line. London Underground proposed sealing the tunnel against leaks by coating its interior with sprayed concrete, a process that would have erased its original appearance entirely. The tunnel was listed at Grade II* on the 24th of March 1995, the day London Underground had scheduled the start of that work. A compromise was reached: one short section was left untreated and the rest received more careful treatment. The route reopened in 1998, later than planned. The tunnel closed again from the 23rd of December 2007 for tracklaying and resignalling. It reopened on the 27th of April 2010 as part of the London Overground network.

• 8. Legacy

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  After the Thames Tunnel proved the concept, several major underwater tunnels followed in Britain: the Tower Subway in London, the Severn Tunnel under the River Severn, and the Mersey Railway Tunnel under the River Mersey. James Henry Greathead played a particularly significant role in refining the tunnelling shield technology that Marc Brunel had pioneered.

  In 1991, the American Society of Civil Engineers and the Institution of Civil Engineers jointly designated the Thames Tunnel an International Historic Civil Engineering Landmark.

  Brunel's original engine house at Rotherhithe, built to house the drainage machinery, now operates as the Brunel Museum. In 2011 a concrete raft was built near the bottom of the Rotherhithe shaft, above the tracks, creating a space whose walls are still blackened by smoke from the steam trains that once ran below. The museum uses this space as a concert venue and occasional bar. A rooftop garden now sits atop the shaft. In 2016 the entrance hall reopened as an exhibition space, with a staircase allowing visitors to descend into the shaft for the first time in more than 150 years.