Thames Tunnel, Rotherhithe to Wapping

The plaque at Rotherhithe station.

London is a city layered with history, and some of the most fascinating stories lie beneath its surface. One such story belongs to the Thames Tunnel, an engineering marvel that was the first tunnel ever successfully built beneath a navigable river and a project so ambitious it took nearly two decades to complete.

Today, you might speed through it on the London Overground, barely giving a second thought to the brick arches passing by your window. But in the 19th century, this passageway connecting Rotherhithe and Wapping was the scene of drama, innovation, and, for a short time, one of the city's most popular tourist attractions.

By the early 1800s, London's docks were booming, but the River Thames created a huge bottleneck. Building a new bridge downstream of London Bridge would have blocked the passage of tall-masted sailing ships. The only solution was to go under the river.

Several attempts to tunnel beneath the Thames had failed disastrously. The soft, treacherous ground beneath the riverbed made traditional mining techniques impossible. Enter the brilliant French-born engineer, Marc Isambard Brunel.

Brunel’s genius lay in his invention of the tunnelling shield. The idea, allegedly inspired by watching a shipworm bore through wood, was a revolutionary concept in civil engineering.

Keilyn at the bottom of the tunnel shaft. Notice the soot mark, from steam trains, still on the wall.

Patented in 1818, the shield was essentially a massive, rectangular, cast-iron frame divided into 36 compartments. Miners would work inside these individual cells, digging away a small section of earth in front of them while the surrounding frame held the unstable ground in place. Once a small segment was dug, the shield would be moved forward, and bricklayers would immediately line the new section of the tunnel behind it. This method was the key to conquering the soft, wet subsoil.

Work began in 1825, but the project was far from smooth sailing. It was a harrowing 18-year ordeal, plagued by financial crises, poor air quality, and most terrifyingly, repeated floods as the river burst through the thin crust of ground above.

Isambard Kingdom Brunel, who would go on to become one of Britain's most famous engineers, started his career working alongside his father, Marc, on the tunnel. In 1828, a major flood nearly killed the young Isambard, forcing the project to be abandoned for six long years due to a lack of funds. It was only after a government loan was secured that work could finally resume, and the twin-arch tunnel was at last completed in 1843.

The tunnel, is a stunning 35 ft (11 m) wide by 20 ft (6.1 m) high and is 1,300 ft (400 m) long, running at a depth of 75 ft (23 m) below the river surface measured at high tide. It was initially intended for horse-drawn carriages. However, the costly ramps needed for vehicle access were never built.

Victorians taking a stroll beneath the River Thames.

Instead, when it opened in 1843, the Thames Tunnel instantly became one of London's must-see attractions. It was a pedestrian walkway, attracting up to two million visitors a year, each paying a penny to walk beneath the river.

Imagine the sight! The tunnel was illuminated by gaslight and lined with stalls selling souvenirs, refreshments, and knick-knacks. It hosted concerts, public dinners, and an annual Fancy Fair with musicians and dancers. It was a true subterranean fairground, a testament to Victorian ingenuity and a source of wonder for the public.

The north entrance through the Windrush line travels.

The novelty eventually wore off, and as a pedestrian toll tunnel, the project never truly recovered its enormous construction costs. In 1865, it was sold to a railway company and was converted for train use.

In 1869, it opened as a railway tunnel, becoming part of the East London Line. Today, this pioneering piece of Victorian civil engineering remains a vital part of London's transport infrastructure, now forming the bedrock of the London Overground networks Windrush line.

The Thames Tunnel is not just a piece of history; it’s a living monument to human perseverance. The next time you're near Rotherhithe or Wapping, remember the two Brunels, the terrifying floods, the ingenious shield, and the curious Victorian crowds who flocked to the world's first and most dramatic tunnel beneath a navigable river.

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