Running between Rotherhithe and Wapping, the quality of Sir Marc Brunel’s masterpiece fills modern engineers with admiration. The tunnel, completed in 1843 after eight years construction, will be an essential link in the new £1 billion East London Railway Line.

Brunel employed his son Isambard - aged just 19 - as resident engineer. It was their first job together, the first tunnel anywhere through soft ground under water, and the oldest tunnel on the present London Underground.

“Victorian brickwork - particularly the early brickwork - was of a tremendous standard,” explains Barrie Noble, construction manager for Transport for London, who is working on the building of the new railway.

The tunnel was relined in the mid-1990s as part of a compromise after a fierce disagreement between London Underground and English Heritage. Some campaigners opposed the relining. But Mr Noble says it gave the tunnel a new lease of life.

“We don’t intend to do anything to interfere with the fabric of the tunnel,” he says. “Brunel and his team and his workmen were excellent.”

The elder Brunel invented a tunneling shield as a way of dealing with the waterlogged soft ground beneath the Thames - a cast iron structure that moved forward as the ground was cut, with bricklayers constructing the double tunnel behind.

It was, as Mr Noble says, “a long way before its time”. With no giant cutting tools, it meant 36 miners, each in his own cell in the shield, removed oak planks one at a time and cut the soil behind to a depth of four inches.

Seven men drowned during the digging - workers had to deal with sudden ignitions of marsh gas and constant inflows of water, including five major floods, in the worst of which Isambard Brunel nearly died.

The existing East London line, including Brunel’s tunnel, closes on the night of 22-23 December, to reopen as part of the new East London Railway from Dalston to West Croydon and Crystal Palace.