IT WAS 30 years ago to the day when one of the greatest feats of engineering history reached its most crucial point. It took five years and 13,000 workers to build - but none of it would have happened without the untiring effort of one Hampshire based man.

During the construction of the Channel Tunnel, all eyes were on Carl Calvert who had the high-pressure job of ensuring the English and French sides met somewhere in the middle.

It could easily have been every engineer and surveyors worst nightmare; the French tunnelling their way towards the White Cliffs of Dover, whilst the English head towards France, both parties oblivious they’ve passed one another.

To prevent that scenario ever happening Calvert worked tirelessly in his Ordnance Survey office, Southampton, liaising with experts in France on a daily basis.

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The Ordnance Survey and their French equivalent were tasked with working out the exact line for the tunnel. Because they worked on the project when it was first proposed in 1974, the existing knowledge granted them a headstart.

However, things weren’t as simple as first hoped - France worked on different grid systems and different sea levels.

Carl and his team had to develop a unique Channel Grid System which covered the tunnel and some of the railway line at both ends.

A mixture of calculations were used, combining the surveying on the ground with satellite system technology.

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Calvert remarked at the time; “It is a bit of a paradox that we have had to look to the skies to work out how we can work underground.

“If you simply dug straight down five metres on each side and went across, then it would miss. One would go over the top of the other.”

During the construction process, Calvert would find himself springing from his bed at 3am to work out calculations and to formulate mathematical equations.

All the work paid off when on December 1, 1990, Britain and France drilled through the final section of rock to join the two halves of tunnel.

Briton worker Graham Fagg and Frenchman Philippe Cozette shook hands through the gap and swapped their nations flags.

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After the successful joining, a British party walked to Calais to get their passports stamped, while a group of French drove to Folkestone, Kent to do the same.

The tunnel was officially opened on May 6, 1994, and has since transported more than 400 million passengers, 80 million vehicles and over 380 million tonnes of freight good - all of that possible because of Calvert.