Hundreds of passengers were forced to flee for their lives after arsonists started an inferno on a moving train.
The vandals, believed to be a man and his girlfriend, are believed to have piled up seats in one of the carriages of the 22.40 Thames Trains service from Banbury to Paddington and doused them in some sort of accelerant before setting them on fire.
The flames quickly took hold and the train was forced to stop. Its passengers were evacuated at Reading as the blaze engulfed the carriage. Metal fittings were melted as temperatures rose to more than 1000 degrees centigrade.
Two fire crews stopped the flames reaching the train's fuel tanks under the next carriage, which would have caused a massive explosion.
Martin Walter, spokesman for Thames Trains, said that the incident on Monday had caused about £250,000 damage. He said: "We believe this was arson and are studying CCTV footage taken from the platforms from all of the stations where the train stopped."
British Transport Police said a witness had reported seeing the man and woman piling up the cushions.