`It was like a tomb down there:

Investigation will focus on decision to halt train and lead victims through tunnel

The investigation underway into the Channel Tunnel fire will concentrate on whether all safety procedures were followed and in particular try to discover why the train was halted.

Safety rules - different for Eurostar and tourist shuttles because they are enclosed and drivers travel with their cars - outline three alternatives for freight shuttle trains.

The first is for the train to continue as fast as possible to an exit. If the fire is too strong, then normal procedure would be for the chef de train to disconnect the locomotive and the club car - where lorry drivers rest - from the remainder of the train and head off fast down the track. That would leave emergency teams, who travel down the smaller service tunnel, to deal with the fire.

The third alternative, which happened on Monday night, is for the train to stop with the club car next to one of the entrances into the service tunnel. These are located at intervals of 375 metres.

Eurotunnel is confident that it has devised set procedures for ensuring that fires can be dealt with easily and an incident such as Monday's was not unexpected. John Noulton, the company's public affairs director, said that initially it was thought there would be a fire once every nine years, but "nowadays, vehicles are much more complex and are at greater risk of starting to burn than old bangers were twenty years ago".

However, the inquiry will have to look at why neither of the first two safety options were taken and why choking lorry drivers had to be evacuated through the tunnel.

The tunnel was designed to be safer than other channel crossings and the risks are said to be the same as for any other rail journey. In a 300-page safety document, Eurotunnel sets out the chance of being killed on a shuttle train as 5.6 per 100 million transits, about 25 times safer than on an aeroplane. An accident in which ten or more people are killed should not happen more than once in every 90 years, and one in which 100 or more people die every 1,100 years.

In some ways, the emphasis on safety has been responsible for the near- bankruptcy of Eurotunnel. As initial plans were being drawn up in the late Eighties, a succession of disasters - such as the Zeebrugge ferry sinking, and rail accidents at Clapham and King's Cross - heightened awareness of the safety risks surrounding a Channel tunnel.

Safety considerations were largely responsible for a railway being built, rather than Mrs Thatcher's dream of a 50-kilometre road tunnel.

But the safety requirements became increasingly onerous, an issue that is still the subject of a legal dispute between Eurotunnel and the British and French governments over the imposition of extra costs which sometimes seemed to cover minute risks.

Privately, though, Eurotunnel must be rather relieved that such onerous requirements were forced on the company, given that it has emerged from its first major incident with no deaths or serious injuries.