The vehicle involved was no. W2437, a British Railways Mark 1 coach which was built in 1960. At this time, trains in the UK were mostly hauled by steam locomotives, which provided steam for heating passenger accommodation. Diesel locomotives of the period were fitted with boilers so that they could be used with existing coaches. However, with steam locomotives gone by the 1970s, and with boilers proving unreliable and expensive to maintain, the decision was made to change to electric train heating (ETH). W2437 was converted in 1976; an electric heater being installed in the vestibule.
The 22:30 sleeping car express from Penzance to Paddington on 5 July 1978 was scheduled to pick up two sleeping cars at Plymouth; this arrangement was so that passengers joining the train there could go to bed without having to wait for the main service to arrive at around midnight.
The main store for bed linen on the Plymouth service was at Old Oak Common depot near London Paddington. Used bedding from Plymouth used to be transported in the guards van of the Plymouth portion, but in 1977 that vehicle was removed from the formation. Instead, the dirty linen was stacked in plastic bags in the vestibule of W2437, against the heater. From then onwards, it was only a matter of time until a serious accident occurred.
The train arrived at Plymouth from Penzance at 23:50. It was coupled up to the Plymouth sleeping cars (which included W2437) and the ETH was turned on at 00:15. The train departed on time at 00:30 and made scheduled stops at Newton Abbot and Exeter. Nobody who saw the train noticed anything amiss, but the bags of linen were now heating up. As they smouldered they began to give off toxic gases, including carbon monoxide. Unfortunately the ventilation system drew fresh air from the vestibule, and the gases were sucked into the system and into each berth.
A major fire developed and the train was stopped at 02:41 near Silk Mill signal box about a mile short of the station in Taunton, Somerset, by the communication cord being pulled. Sadly, most of the victims were already dead from carbon monoxide poisoning. A small number of passengers awoke and were able to escape, although they had considerable difficulty in doing so due to the smoke and heat. The sleeping car attendant of the Plymouth coaches could only shout a warning to a few of the occupants before he was overcome by smoke; it was the attendant in the adjacent coach who pulled the communication cord. The victims as well as other injured passengers were taken to the nearby Musgrove Park Hospital for treatment.
A twelfth passenger, a Belgian national, died from pneumonia nine months later, having never regained consciousness.
Initial reports showed that fire crews had difficulty during the rescue operation because doors on the train were locked. This was against the rules, but it was commonplace for attendants to lock the end doors of the pair of coaches that they were responsible for. This meant that attendants could greet passengers on arrival, and it helped to keep out intruders. Following this discovery, BR made it absolutely clear that all doors were to be left unlocked at all times.
The Taunton fire occurred just as new Mark 3 sleeping cars were at the design stage. The decision was taken to install state-of-the art fire prevention measures including sophisticated warning systems, fire retardant materials, multilingual warning placards and revised emergency procedures.
The old Mark 1 sleeping cars were phased out by the early 1980s, and so far the Mark 3s have had an excellent safety record.