Sorry, this video asset has been removed.

The staggering scale of the challenge facing Channel Tunnel engineers following the September fire became clear on Wednesday when the damaged section was shown to the media for the first time.

After announcing that the tunnel would fully re-open in mid-February, Eurotunnel chief executive Jacques Gounon led visitors to what had been a scene of devastation on September 11.

An apparent lorry fire on a freight shuttle seven miles into the tunnel from the French side sparked a raging inferno.

Thirty two drivers and shuttle crew were led to safety.

A hundred and twenty feet under the sea bed hundreds of workmen are working around the clock in this underground construction site to repair the half-mile stretch of tunnel.

Concrete linings destroyed by 1,000 degree heat have been replaced and are being sprayed with new cement.

It is an amazing world of wind, noise, dust, lights and scaffolding.

Four thousand tonnes of concrete and 3,000 tonnes of ballast are being used in the project.

The four-month project is costing Eurotunnel £50 million, but bosses hope to recoup that sum when they know who or what was responsible for the fire.

The south running tunnel was re-opened 30 hours after the fire, but there has been a restricted service ever since.

The damage has cost Eurotunnel up to £100 million in lost revenue.

The fire is still being investigated but M Gounon said new safety measures were being introduced or recommended to officials.

Customers should not be concerned about travelling through the tunnel after it reopens, he said.

"Safety remains our key priority," he said. "Since the opening of the tunnel, thank God, we haven't experienced any fatality in the tunnel. When you consider the first fire (in 1996) was a malicious act this was the first real fire since the opening of the tunnel."

He continued: "Once we resume traffic in February we will see customers coming back to the levels we had before."