King's Cross Fire - Investigation and Report

Investigation and Report

A public inquiry into the incident was conducted by Desmond Fennell, OBE QC, assisted by a panel of four expert advisers. The inquiry opened at Central Hall, Westminster on 1 February 1988 and closed on 24 June, after hearing 91 days of evidence.

Although smoking had been banned on underground sections of the London Underground in February 1985 (a consequence of the Oxford Circus fire), the inquiry found the fire was most probably caused by a traveller discarding a burning match that fell down the side of the moving staircase on to the running track of the escalator. The possibility that the fire had been started deliberately was discounted by police, as there was no evidence that an accelerant had been used and access to the site of the fire was difficult. Investigators found charred wood in eight places on a section of skirting on an escalator and matches in the running track, showing that similar fires had started before but had burnt themselves out without spreading. These combustion points were on the right-hand side, where standing passengers are most likely to light a cigarette (passengers stand on the right to let walking passengers pass on the left). Smoking on Underground trains was banned in July 1984 and following a fire at Oxford Circus station the ban was extended to all underground stations but smokers often ignored this and lit cigarettes on the escalators on their way out. The investigators found a build-up of grease under the tracks, which was believed to be difficult to ignite and slow to burn once it started, but it was noted that the grease was heavily impregnated with fibrous materials. A test was conducted where lit matches were dropped on the escalator to see if ignition would occur. Matches dropped did ignite the contaminated grease and the fire began spreading, being allowed to burn for nine minutes before being extinguished.

This test replicated the initial eyewitness reports up to that point but four expert witnesses could not agree as to how the small fire flashed over, with some concern that the paint used on the ceiling had contributed to the fire. A model of King's Cross station was built at the Atomic Energy Research Establishment using computer simulation software; this showed the flames first spreading along the floor of the escalator, rather than burning vertically and suddenly producing a jet of flame into the ticket hall, matching the tube fire. A fire behaved as in the computer model during experiments with a third scale replica of the escalator. The metal sides of the escalator contained the flames and directed hot air ahead of the fire. Sensors indicated that wooden treads for 20 feet in front of the flames quickly reached between 500°C and 600°C. When the treads of the escalator flashed over, the size of the fire increased exponentially and a sustained jet of flame was discharged from the escalator tunnel into the model ticket hall. The conclusion was that this newly discovered trench effect had caused the fire to flashover at 19:45.

London Underground were strongly criticised in the report for their attitude to fires underground, underestimating the hazard because no one had died in a fire. Staff were expected to send for the Fire Brigade only if the fire was out of control, dealing with it themselves if possible. Fires were called smouldering and staff had little or no training to deal with fires or evacuation.