These are the secrets of the Channel Tunnel as the historic hole turns 30

It is almost 30 years to the day since the opening of the Channel Tunnel – the first to connect Britain to mainland Europe.

After six years of hard work, the longest undersea tunnel in the world opened – and thirty years on, it still helps transport millions of commuters each year from the Strait of Dover to France.

Although plans to build the channel tunnel were suggested as early as 1802, they didn’t come to fruition until the 1980s...