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The Thames Tunnel – The World’s First Underwater Tunnel

Plagued by floods, fires and gas leaks – horribly overdue and over budget – and resulting in the death of seven people, this was the epic battle to build the world’s first underwater tunnel. 

To say that the construction of the Thames Tunnel was a tortuous undertaking would be a glorious understatement. Nobody had ever successfully tunnelled beneath a river before and this was one project that would shoulder the burden of progress and the many mistakes made along the way.

This is a story about construction unbridled by health and safety regulations, the kind of bludgeoning, relentlessly ambitious project that often emerged during Victorian-era Britain and that completely transformed the country. Not only that, it set a method and precedent for building underwater tunnels that have roughly continued to this day. A titanic achievement, but a gruelling path to completion. 

The Center of the World 

London in the early 19th Century was bursting at the seams. The capital of an empire that stretched around the world and a financial centre with unmatched clout and ambition. Its docks were some of the busiest in the world with goods arriving from all corners of the empire, but London had begun to sag under its own success. 

Those who complain about London’s traffic today should really spare a thought for those plying their trade on the hellish, dangerous, badly kept roads of the 19th Century. With small streets crammed with carts, horses, pedestrians, animals and who knows what else, it was not a setting befit of the richest city in the world. 

While goods could be transported to and unloaded from the port with relative ease, the journey out from London was quite another matter. Even the relatively simple act of crossing the Thames could take several hours, with the iconic London Bridge, built in the 12th Century, taking the brunt of the traffic. If only there was another way that would perhaps not need to go over the river, but beneath it instead. 

The Tunneling Fiascos

Nowhere in the world existed a tunnel beneath a river and after two recent disastrous attempts nearby, many had reservations it could ever be done. 

In 1798, a venture to dig a tunnel under the Thames between Gravesend and Tilbury, east of London, commenced despite numerous reservations surrounding the plans. Two vertical shafts were dug at either end of the planned route but engineers faced a fierce battle from the get-go. Steam engine water pumps were brought in to desperately keep the water out of the shafts but to no avail. The shafts repeatedly flooded eventually causing the whole project to be abandoned in 1802, with little more to show than two very mini tunnels dug and a small fortune spent. 

The next attempt came in 1805 with a proposed route between Rotherhithe and Limehouse in London itself. To be fair, this one did a lot better and a group of Cornish miners managed to dig out a 305 metres (1000 ft) long tunnel measuring 61–91 cm by 1.5 metres (2–3 feet by 5 feet) under the Thames. This small tunnel was only designed to be a pilot tunnel to what would come next, but after it flooded twice, the project was abandoned in 1809. It led engineers to conclude that “an underground tunnel is impracticable.”

Marc Isambard Brunel

Enter c- or should I say Sir Marc Isambard Brunel as he would later become – a French-born engineer with bursting ambitions. Born in Normandy in 1769, Brunel fled the French Revolution and wound up in the United States where he eventually rose to become the Chief Engineer in New York City. In 1799, he moved to London where he was finally reunited with his English wife, who had remained in France when he was in the U.S and had come close to execution during the reign of terror that swept the country between 1793 and 1794. 

Brunel was no doubt a talented engineer but one with a poor business sense to boot. In 1814, he proposed a tunnel under the River Neva in St Petersburg but was turned down by Emperor Alexander I of Russia. By 1821, after a series of failed enterprises, he found himself deep in debt, as was eventually sentenced to King’s Bench Prison, a debtors’ prison in Southwark – a place where they were kind enough to allow the family to come along for the ride – I’m honestly not sure if that’s better or not. 

After the British government discovered that Brunel had begun communicating with the Tsar over the possibility of emigrating to Russia and no doubt stung that they were about to let a supremely talented engineer slip through their finger, it agreed to pay the £5,000 (£561,000 today) to clear his debts, leaving Brunel and his family free. 

And as they say, the rest is history.  

The Tunneling Shield  

Shortly after the failure of the 2nd Thames tunnel, Brunel was strolling beside the river when he stopped to inspect a piece of rotten ship’s timber that had floated ashore. After peering through his magnifying glass and identifying that the wood had been attacked by shipworm – tiny marine molluscs that burrow through wood, consuming the timber itself but excreting a residue that lines the tunnels – he was struck by an idea that would revolutionize tunnel building. 

Taking inspiration from the dreaded shipworm, Brunel designed the Tunneling Shield, a grid of iron frames that could be placed against the face of the tunnel to prevent it collapsing. The framework itself was supported by wooden planks running horizontally and the entire structure was broken into 36 cells, each measuring 0.9 metres (3 ft) wide and almost 2.1 metres (7 ft) tall which could all be independently inched forward and open and closed.  

The working face of the tunnel shield was 78.9 sq metres (850 square feet), while the entire structure weighed a hefty 90 tons. Above the tunnelling shield were a series of iron plates that acted as a temporary roof, providing much-needed safety for those working on the face. This entire contraption would be slowly pushed down the tunnel as excavation work continued behind and brickwork could be laid along the tunnel walls.  

The beauty of the tunnelling shield was that the wall beyond each cell could be cut back, while the rest remained closed and so retained the wall’s stability. Before Brunel’s invention, miners would simply hack at the tunnel face, which was effective, but could prove deadly when it destabilized the entire wall. 

Now, this might not all sound particularly revolutionary, but it completely changed how tunnels were dug and the same basic method has been used ever since. 


If the two failed tunnelling attempts had led many to assume digging beneath a river could never be done, Brunel’s tunnelling shield changed quite a few minds. A tunnel beneath the Thames was seen as the perfect test and Brunel produced a plan to build a link between Rotherhithe and Wapping. 

The project garnered significant interest and Brunel was soon able to raise the funds needed through a public subscription with some substantial private donations, notably from the Duke of Wellington. Soil samples were taken from both sides of the Thames, as well as the river bed itself, and the decision was taken to try and tunnel as close to the bottom of the river as possible to try and mitigate the possibility of running into the dreaded quicksand below. 

The depth was a matter of fine margins, the lower you went there was less risk of the river bed collapsing into the tunnel, but was countered by the danger of going too deep and attempting to build through mushy quicksand – which you probably don’t need me to tell you is far from ideal. The final plan submitted called for a tunnel that would be 11 metres (35 ft) wide by 6 metres (20 ft) high, 396 metres (1,300 ft) long, and reach a lowest depth of 23 metres (75 ft). 

Construction Begins

Before any tunnelling below the river could begin, the first shaft had to be dug, which would be on the south bank of the river at Rotherhithe, 46 metres (150 ft) back from the river. But again, this wasn’t simply men hacking into the ground. A large iron ring, 15 metres (50 ft) in diameter, was set on the ground, and on top, a brick wall 12 metres (40 ft) high and 91 cm (3 ft) thick was constructed. Once completed, the soil beneath the ring was slowly excavated which caused the entire brick structure to gradually slide down into the earth and so creating the perfect shaft wall. 

All was going well until the structure refused to sink any further, requiring an extra 50,000 bricks to be added to push the wall down to its desired depth. Eventually, Brunel realised that the problem was down to the sides running parallel to each other which caused a build-up of pressure. When the shaft on the Wapping side was eventually built years later, he adopted more of a cone shape which seemed to work perfectly.

Once the Rotherhithe shaft was completed, the individual pieces of the tunnelling shield were hauled down and assembled below. The project was about to strike out towards the Thames. 

Slow Hazardous Work  

Before getting to the treacherous working conditions, we should probably introduce another pivotal figure working on the Thames tunnel – and other Brunel. The phrase like father like son is entirely appropriate here because alongside Marc Isambard Brunel during the process was his 20-year-old son Isambard Kingdom Brunel, a young whippersnapper learning the trade from his old man, but who would himself go on to become one of the greatest engineers of the 19th Century, designing railways, ships, shipyards, tunnels and bridges. In 2002, a public poll was conducted in the UK to rank the ‘100 greatest Britons’ and would you know it, Brunel Jr came in 2nd. 

And if you get all the way to the end of this video I’ll even tell you who was number 1. 

Anyway, back to the gruelling work beneath the Thames. The Tunneling Shield was hugely successful but work remained painfully slow with the kind of working conditions that health safety officers today would lose their mind over. Much of the problem came from the toxic state of the river. Today, the River Thames is remarkably clean for a city the size of London, but in the early 19th Century, it was a cesspool of unspeakable horror.

Sewage that leaked into the tunnel often contained methane gas which could be ignited by the oil lamps being used while filthy water itself caused severe illness to many working underground, including Marc Brunel and the resident engineer, John Armstrong, who became so ill he was replaced by Brunel Jr – who remember was just 20 years old at the time. Symptoms ranged from severe headaches, diarrhoea and even temporary blindness, while one man even died as a result.   

The tunnel was inching forward at a tepid rate of around 3–4 metres (8–12 ft) per week, slower than expected which raised the problem of the dwindling finances attached to the project. The solution was remarkably simple – charge the public one shilling to descend the shaft and into the tunnel to watch the Tunnelling Shield in action. Nowadays I don’t know how many takers you would have willing to pay to stand in a crap infested tunnel watching men hack into a wall, but this was the 1820s and long before the internet, TV and even radio, ways to pass the time were few and far between. The tunnel received an extraordinary 600 to 800 visitors per day, which shows that actually quite a few people rather enjoyed standing in a crap infested tunnel watching men dig a tunnel and the scheme at least kept the work going.   


As the tunnel inched out further into the Thames, a series of floods nearly derailed the entire operation. In 1826 the tunnel flooded to a depth of 3.6 metres (12 ft) but pumps eventually cleared the water and work resumed. However, the following year, on 18th May 1827 with the tunnel at 167 metres (549 feet), a gusher – that’s mining lingo for a major leak – erupted from one of the cells in the Tunneling Shield. In theory, this could be stopped by closing the cell in question, but the force of the water was so strong that it sent miners scurrying for ladders to escape the rising water. 

The problem was that the tunnel had passed beneath a cavity in the river bed causing it to collapse and leaving a hole into the tunnel. Brunel’s response was remarkably rudimentary when you think about it but certainly worked. By dropping 566 cubic metres (20,000 cubic feet) of earth from a boat directly over where they assumed the cavity to be, they were able to seal the hole and two weeks later water pumps began clearing the flooded tunnel. The project had survived its first major setback, but the next would prove catastrophic. 

Stop Work

On 12th January 1828 water once again began flooding into the Thames Tunnel. Men scrambled to safety, but this time, the water rose too quickly. Six men never made it out alive that day, and the young Brunel only just escaped with his life. Having run to the emergency hatch that was always kept locked – what did I tell you about health and safety – by some remarkable stroke of luck, somebody from the outside heard Brunel’s frantic calls moments before he lost consciousness. The hatch was opened and the half-dead man was dragged out and resuscitated. 

The incident left a dark shadow over the project and with another massive amount of earth needing to be purchased then dispatched to depths of the Thames to plug the cavity, it left Brunel utterly broke once again. Unable to finance the excavation work any longer, digging stopped inside the Thames Tunnel and the face was bricked up. 

Perhaps the doubts over tunnelling beneath a river were justified after all as it was seven long years until work began again. 


In that time Brunel worked feverishly to secure funding to complete the tunnel but enormous question marks had emerged and the government were doubtful it could ever be completed. He finally secured £247,000 (around £32.8 million today) from the Treasury in December 1834 and work commenced shortly after with a new model Tunneling Shield that provided better protection on the tunnel wall.  

Work staggered on slowly but surely for another six years, running the disaster gauntlet all the way with yet more flooding, gas leaks and the odd fire, until the Thames Tunnel finally arrived at Wapping on the north side of the river in November 1841, and where another shaft was dug to provide access. It had taken 16 years and seven lives, but the world’s first underwater tunnel was finally complete. If you detract the time when the work had stopped, it meant the tunnel moved forward on average just 10 cm (4 inches) per day. A painstaking, grinding achievement. 


Sadly it would take some time until the tunnel reached its full potential. With funds once again exhausted, there was nothing left to build the approaches on both sides that would have allowed horses and carts to pass through as planned. Instead, the hugely expensive tunnel became pedestrian-only, again with the public paying to use it. 

It included lighting and roadways, while the shafts on either side had elaborate and finely decorated spiral staircases added. It was a charming tunnel, but with the pedestrian entrance fees barely covering the government’s loan interest, it proved to be far from economically viable. The project had cost a whopping £454,000 (roughly £60 million today) to dig and another £180,000 (£20 million today) to add the finishing touches and had effectively become a tourist attraction that was often frequented by drunks and the homeless who would take refuge beneath the arches, earning the tunnel the nickname, the Hades Hotel. It was, no doubt, far from the stately tunnel that had been planned.  

But salvation came in the form of a blossoming industry that was sweeping the nation – the railway. In 1865 the tunnel was purchased by the East London Railway Company who intended to build a railway link between Wapping and the South London Line which ran trains to the south of England. 

In just four years the tunnel was repurposed with railway tracks running through and entrances added on both sides. The first train to run through the Thames Tunnel came on the 7th December 1869 and it hasn’t looked back since. This line was eventually absorbed into the London Underground becoming the East London Line and today forms part of the Overground network – which yes sometimes also runs underground. 


The construction of the Thames Tunnel proved far more arduous than anybody would have imagined, especially Brunel. And while it would take some time to fulfil its potential, it was nevertheless a trailblazing achievement that proved that such a project beneath rivers could be completed.

Not long after completion, another tunnel, the Tower Subway crept beneath the Thames while similar examples began springing up around Britain, including the Severn Tunnel under the River Severn, linking Gloucestershire in England and Monmouthshire in Wales and the Mersey Railway Tunnel under the River Mersey in Liverpool. The Thames Tunnel had sparked a revolution, rivers had been tamed, and Victorian Britain couldn’t get enough of it.

And for those who have held on until the bitter end, the Greatest Briton ever according to the 2002 public poll – Sir Winston Churchill.  

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