Why wasn't it built before?
It was technically possible to build a Channel Tunnel for well over a century before it was finally built. Why the delay?

First impractical suggestions in the Napoleonic Wars
Two centuries ago, the idea of a road tunnel was suggested to Napoleon during a brief peace between France and England in 1802. But war soon broke out again: the cartoon left is a joke, showing invading French troops walking under the sea in a road tunnel and flying over in balloons (the channel was first crossed by hot-air balloon in 1785).

Both schemes existed only on paper. They lacked the technology to overcome the problems, and did not have the necessary geological knowledge. They guessed that the chalk of Cap Blanc Nez ran under the sea all the way to the white cliffs of Dover - no-one really knew. They imagined horse-drawn carriages driving down a wood-propped tunnel like mines of the day, lit by candles.

A railway tunnel - a cure for seasickness!
The first steam locomotives hauled passenger trains in the 1820's. By 1850 , steam railways were running most of the way from Paris to Calais, and from London to Dover. Crossing the stormy channel in the small ferries of the day was the part of the journey that most travellers dreaded.

Victorian engineers thought they could do it!
By this time, engineers had much more experience of major tunnelling works. Many main line railways had long tunnels. They had also worked underwater - Brunel completed a footway tunnel under the Thames in 1843 - an 18 year struggle with flooding. A submarine telegraph cable was laid across the Straits of Dover in 1851. Elsewhere, a 5-mile tunnel through the peaks of the Alps was started in 1857, and the Suez Canal - the proudest feat of 19th century engineering - opened in 1869.

Confident French and English engineers now approached the task of planning to construct a 25-mile undersea tunnel in earnest..... Back to top

 
French engineer Thomé de Gamond and his railway tunnel scheme of 1857 - then steamship ferries carried 350,000 passengers a year, 3/4 of them English. He estimated the appeal of a 25 minute undersea crossing with no seasickness would attract double the number - including many more Continentals.

The problems tunnellers faced:

• geology - they had to check, and hoped to find that a suitable rock for tunnelling stretched in an unbroken bed across the channel;
• ventilation - how to stop smoke from the steam trains choking the passengers in such a long tunnel?
• defence - the English were worried about creating an easy route for invaders to cross the Channel.

Frenchman Thomé de Gamond worked hard to find convincing answers:
in 1857 his scheme was widely accepted in England and France. After making many hazardous solo dives to check the sea-bed, he proposed a rail tunnel, bored through the chalk which he believed ran below the sea-bed.

His plan - see left - had an international port built mid-way on an artificial island on the Varne sandbank. Steam trains would run from the Paris-Amiens-Boulogne line on a double track through a single gas-lit tunnel. Ventilation was provided by the mid-way opening at the Varne. Back to top

First serious attempts to build a tunnel
The private railway companies either side of the channel could now afford to put up the money for a serious attempt - IF their governments would permit it. Railway barons dreamed of a profitable long-distance railway not just across the Straits of Dover, but across Europe - which would generate huge volumes of new passenger and freight traffic!

1870's: checking the geology
England and France became quite friendly after the Franco-Prussian war 1870-71. The cocky French had been badly beaten; Paris had been beseiged, and a triumphant German Kaiser was seen as a newly-powerful common enemy.

Both countries agreed to work together on a joint tunnel scheme to bring them closer together. With government approval, tunnel companies were set up to do the first serious scientific exploration of the geology - to find out just what rocks lay under the sea bed between Dover and Calais....

The Lower Chalk bed proved the best part of the chalk for tunnelling: it is....

• soft but firm - easy to dig, but will stand up even without supporting walls
• waterproof - it is 80+% chalk, with some clay mixed in
• thick enough to hold a tunnel

1. 1876: French Channel Tunnel Company uses the paddle steamer "Ajax" to take samples from the seabed to check the geology was suitable for tunnel.

2. 1870's - on land, shafts were dug to check the chalk underground. There were no problems at Sangatte on the French side, but at St. Margarets (east of Dover), the shaft flooded through cracks in the chalk. They switched work to west of Dover.
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 1880-83: trial tunnels dug either side
  
1. Engineers began boring trial tunnels from both sides in 1881: this is the English site, at the bottom of Shakespeare Cliff.
2. Both sides used improved tunnel boring machines, first patented in 1875.
  
3. In 1882 the English Tunnel Company faced political opposition: the two governments had quarrelled over the Suez Canal and colonies in Africa. VIP visits were arranged in an attempt to get British government permission to complete the work - but the British army objected. Here influential visitors head for the workface on a workmen's train.
4. .At the undersea end of the tunnel: VIPs inspect the boring machine in action - chalk slurry pours out from a conveyor belt at the rear, while the cutting heads in front dig into the chalk rock.

A technical success?
The two tunnel companies started digging seriously in 1881 from the cliffs between Dover and Folkestone, and west of Calais (Sangatte).

Technically, it was a success - driven by compressed air, the boring machines worked well, and there was so little flooding they only switched the pumps on for half a day every two weeks! Within the first year, each side had bored almost 2 km of tunnel, and they expected to complete a 7 foot diameter pilot tunnel across the Channel within 5 years.

They planned the tunnel trains would also be powered by compressed air - solving the problem of smoke and fumes. Soon the invention of clean electric trains offered an even better solution.

Tunnel abandoned - fear of a French invasion
This aroused alarm amongst the British military, and in 1883, further building of the Tunnel was banned. The Tunnel company suggested (in vain) that, as a safeguard, they could instal an inlet to the sea half-way along the tunnel! A soldier would be permanently on guard, ready to pull the plug if the French should try a surprise invasion! They offered to build a fort guarding the tunnel entrance, and to wire it up with explosives ready to destroy the whole tunnel or flood it with seawater.....

It was no good! The British generals did not trust the French, and that was that. The French tunnellers gave up - believing the British would always be stubborn about staying as an "island fortress".

Meanwhile on the Dover side, though the Tunnel was abandoned, they drilled their shaft deeper and in 1890 discovered coal and iron-ore seams - hidden extensions of the coalfields of northern France and Belgium: see Formation of coal)
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1914-18 - the tunnel could have supplied the Trenches
The generals now wished the Tunnel had been built!

During the First World War, fresh troops, munitions and supplies had to cross the Channel under constant fire from enemy ships, submarines, airships and aircraft - needing the protection of the Dover Patrol. Wounded soldiers were also in danger returning home from the Front.

It was estimated that the Tunnel could have shortened the war by 2 years - in fact, the Germans might not have invaded France if the Tunnel had been built! As it was, the Germans very nearly won.....

More talking - no action
After the First World War, many politicians were in favour of going ahead with a tunnel, and there were more trial borings in the 1920's - but behind the scenes, generals and diplomats who still mistrusted the French quietly vetoed the scheme. Back to top

Over the years, bridges as well as tunnels were proposed. The big snag was the danger to shipping, especially in the foggy turbulent Straits of Dover.

1974-75: the second attempt
In 1973, Britain finally joined France in the Common Market AND both governments agreed to have another go at building a tunnel. But in 1975, construction was again abandoned because the British prime minister (Harold Wilson) had to look for economies in a financial crisis caused by dramatically rising world oil prices.

1987-94 - third time lucky!
Finally in the 1980s the British and French governments commissioned more studies, and decided that a "traditional" rail tunnel would be least risky and best value for money - just as could have been built a century ago, or 20 years ago, for a fraction of the price! They gave the go-ahead to a private company using private money to build a rail tunnel.

Work stated on both sides in 1987, and the fixed link was opened in 1994 - nearly 2 years late, and way over budget.

...but the tunnel doesn't kill the ferries
It was correctly predicted that cross-channel traffic was growing so fast that there would be enough business for both the tunnel and the ferries - who survived by combining forces, concentrating on the Dover-Calais route, and investing in giant super-ferries that could offer cheaper fares. Back to top

Checking the geology AGAIN
1980's engineers used new technology developed for deep-sea oil exploration to check exactly what was under the sea bed.

 
1. Cross-section of the geology as known today - showing the present tunnel, which follows the Lower Chalk most of the way across, except for the under-land tunnel on the French side.
2. They found hazardous "buried valleys" on the sea bed, filled with mud and sand rather than solid rock. The tunnel route had to keep to solid rock.
See 'How the Channel was formed' for more about the geology. Back to top

How the Tunnel operates
There are two single-track rail tunnels, and a third smaller service tunnel as an emergency exit (with frequent cross passages). These were bored through the chalk from either side, and met in the middle. They are lined with concrete panels (on the French side, made from the Marquise quarries).

The tunnel copies some of the Alpine mountain tunnels in carrying cars and lorries on drive-on/drive-off shuttle trains. Operated by Eurotunnel "le Shuttle", these share the tracks with high speed long-distance passenger trains run by Eurostar. All trains are electric, and the twin tunnel While the vehicle shuttle competes head-on with the ferries, Eurostar trains regard their main competitor as the airlines. They charge fares to match airline business tickets, and soon siezed 80% of the London-Paris market. Back to top

High speed rail links
In 1993 a high-speed rail link opened from the French-side Tunnel portal to Lille, and from there to Paris and (more recently) Brussels. Eurostar trains had to "crawl" through Kent at 70 miles an hour on normal suburban lines, speeding up once they reached the Tunnel and racing through the French countryside.

On the English side, the first stage of a purpose-built line from the Tunnel to London is planned to be open in 2003 (see links below)

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Future schemes: a drive-through tunnel for cars? ...or a second rail tunnel for Eurostar passenger trains and the vehicle-carrying shuttle

A second tunnel?
As part of the conditions under which the Tunnel Company were granted a monopoly for 25 years, they had to produce a feasability study for a second tunnel.

Although cross-channel traffic is increasing steadily, and the first tunnel covers its running costs, it has made slow progress in paying off its enormous debt from the construction. No-one is likely to be keen to build a second tunnel in the near future - so this feasabilty study will probably go no further.

A road or rail tunnel?
Technology has improved so much that it would now be possible to consider a larger bore drive-through tunnel for cars (lorries emit too much fumes) as an alternative to one carrying extra train tracks. Back to top

More information and Weblinks

Building the high-speed rail link from the Channel Tunnel to London: www.ctrl.co.uk

Places to visit:
Transmanche Museum, Cap Blanc-Nez

Related background information
How the Channel was formed
Formation of coalfields
Dover Patrol: guarding the Channel in two World Wars
Ferries
First crossings - how pioneers crossed the Straits of Dover

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