The Channel Tunnel (French: Tunnel sous la Manche), sometimes referred to as the Chunnel, is a 50.46-kilometre (31.35-mile) railway tunnel beneath the English Channel which connects Folkestone in the United Kingdom with Coquelles in northern France. Opened in 1994, it remains the only fixed link between Great Britain and the European mainland.
The tunnel has the longest underwater section of any tunnel in the world, at 37.9 km (23.5 miles), reaching a depth of 75 m (246 ft) below sea level and runs, on average, 45 m (148 ft) below the seabed. It is the third-longest railway tunnel in the world. Although the tunnel was designed for speeds up to 200 km/h (120 mph), trains are limited to a maximum speed of 160 km/h (99 mph) for safety reasons. It connects to high-speed railway lines on either end: the LGV Nord in France and High Speed 1 in the United Kingdom.
The tunnel is operated by Getlink (formerly Eurotunnel) and is used by Eurostar high-speed passenger trains, LeShuttle services for road vehicles, and freight trains. In 2017, Eurostar trains carried 10.3 million passengers, freight trains transported 1.2 million tonnes (2.6 billion pounds) of freight, and LeShuttle trains moved 10.4 million passengers in 2.6 million cars and 51,000 coaches, and 1.6 million heavy goods vehicles carrying 21.3 million tonnes (47 billion pounds) of freight. That compares with 11.7 million passengers, 2.2 million cars, and 2.6 million heavy goods vehicles transported by sea through the Port of Dover.
Proposals for a cross-Channel tunnel date back as early as 1802, but concerns over national security delayed development. The modern project was initiated by Eurotunnel in 1988 and completed in 1994, at a final cost of £4.65 billion (equivalent to £9.8 billion in 2025). An engineering marvel, the Channel Tunnel was, at the time of its opening, by far the longest tunnel in Europe, and has only been surpassed by the Gotthard Base Tunnel in Switzerland. However, despite its engineering significance, several economic assessments have found that it has had only a limited positive economic impact on the British economy. Additionally, the tunnel has also experienced occasional service disruptions due to technical faults, fires, severe weather, and unauthorised access by migrants around Calais seeking entry to the United Kingdom.
In 1802, Albert Mathieu-Favier, a French mining engineer, proposed a tunnel under the English Channel, with illumination from oil lamps, horse-drawn coaches, and an artificial island positioned mid-Channel for changing horses. His design illustrated a bored two-level tunnel, with the upper tunnel to be used for transport, while the lower tunnel for groundwater flows.
In 1839, Aimé Thomé de Gamond, a Frenchman, performed the first geological and hydrographical surveys on the Channel between Calais and Dover. He explored several schemes and, in 1856, presented a proposal to Napoleon III for a mined railway tunnel from Cap Gris-Nez to East Wear Point with a port/airshaft on the Varne sandbank at a cost of 170 million francs, or less than £7 million.
In 1865, a deputation led by George Ward Hunt proposed the idea of a tunnel to the Chancellor of the Exchequer of the day, William Ewart Gladstone.
In 1866, Henry Marc Brunel surveyed the sea floor of the Strait of Dover. The results of his survey proved that the sea floor was composed of chalk, like the adjoining cliffs; therefore, the construction of a tunnel would be technically feasible. For this survey, he invented the gravity corer, which is still used in geology.
Around 1866, William Low and Sir John Hawkshaw promoted tunnel ideas, but apart from preliminary geological studies, none were implemented.
An official Anglo-French protocol was established in 1876 for the construction of a cross-Channel railway tunnel.
In 1881, British railway entrepreneur Sir Edward Watkin and Alexandre Lavalley, a contractor of the French Suez Canal Company, participated in the Anglo-French Submarine Railway Company, which conducted exploratory work on both sides of the Channel. From June 1882 to March 1883, the British tunnel boring machine tunnelled, through chalk, a total of 1,840 metres (6,037 ft), while Lavalley used a similar machine to drill 1,669 m (5,476 ft) from Sangatte on the French side. However, the cross-Channel tunnel project was abandoned in 1883, despite this success, after fears raised by the British military that an underwater tunnel might be used as an invasion route. Nevertheless, in 1883, this TBM was used to bore a railway ventilation tunnel—7 ft (2.1 m) in diameter and 6,750 ft (2,060 m) long—between Birkenhead and Liverpool, England, through sandstone under the River Mersey. These early works were encountered more than a century later during the TransManche Link (TML) project.
A 1907 film, Tunnelling the English Channel by pioneer filmmaker Georges Méliès, depicts King Edward VII and President Armand Fallières dreaming of building a tunnel under the English Channel.
In 1919, during the Paris Peace Conference, British prime minister David Lloyd George repeatedly promoted the idea of a Channel tunnel as a means of reassuring France that Great Britain was ready to defend the French people against a possible German attack. The French did not take the idea seriously, and nothing came of the proposal.
In the 1920s, Winston Churchill advocated for the Channel Tunnel, using that exact name in his essay "Should Strategists Veto The Tunnel?" It was published on 27 July 1924 in the Weekly Dispatch, and argued vehemently against the idea that the tunnel could be used by a Continental enemy in an invasion of Britain. Churchill expressed his enthusiasm for the project again in an article for the Daily Mail on 12 February 1936, "Why Not A Channel Tunnel?"
There was another proposal in 1929, but it did not materialize, and the idea was abandoned. Proponents estimated the construction cost at US$150 million. The engineers had addressed the concerns of both nations' military leaders by designing two sumps – one near the coast of each country – that could be flooded at will to block the tunnel, but this did not appease the military or dispel concerns about hordes of tourists who would disrupt English life.
A British film from Gaumont Studios, The Tunnel (also known as TransAtlantic Tunnel), was released in 1935 as a science fiction project concerning the creation of a transatlantic tunnel. It briefly referred to its protagonist, a Mr. McAllan, as having completed a British Channel tunnel in 1940, five years after the film's release. What was kept quiet at the time was the advisory involvement of Harold, later Sir Harold, Harding then working for Mowlem as he believed it to be far-fetched, although he was to become a life-long advocate for a twin-bored tunnel, running the British site investigations as part of the 1960s feasibility study and continuing to lobby the Thatcher government in the decision-making years.
Military fears continued during World War II. After the surrender of France, as Britain prepared for an expected German invasion, a Royal Navy officer in the Directorate of Miscellaneous Weapons Development calculated that Hitler could use slave labour to build two Channel tunnels in 18 months. The estimate caused rumours that Germany had already begun digging.
By 1955, defence arguments had become less relevant due to the dominance of air power, and both the British and French governments supported technical and geological surveys. In 1958, the 1881 workings were cleared in preparation for a £100,000 geological survey by the Channel Tunnel Study Group. The British side was run by Harold Harding, with René Malcor running the French operations. 30 percent of the funding came from Channel Tunnel Co Ltd, the largest shareholder of which was the British Transport Commission, as successor to the South Eastern Railway. A detailed geological survey was carried out in 1964 and 1965.