mail to stop. The station, however, was occupied by the shunting goods train and therefore his signals stood at danger. He accepted the mail at 5:14 am. The signals at Charfield should have been at danger, since the block system employed left no room for human error on the signalman's part. The outer home signal (which was at danger) at Charfield, was fitted with a track circuit. The GWR goods train was nearly clear of the line and the Westerleigh empty up goods train was approaching from Wickwar, when Button happened to notice the indicator for this track circuit. It changed to 'occupied', but then Button then saw to his alarm the indicator fly back to 'clear' again. This could mean only one thing: the mail had failed to stop at the signal. Having not heeded the distant signal which should have been at caution, Aldington and Want of the mail had assumed the line to be clear and had passed the home signal at around sixty miles an hour. To make matters worse Button had accepted the up goods train, which was approaching the road bridge. There was no error in Button's part in doing this, but it meant that the mail was running into a bottleneck – the track was in a cutting with a road bridge spanning both main lines, the sidings cutting off at the road bridge. Both main lines were blocked. Prevention The report on the accident by Colonel Pringle stated that the LMS conversion from gas to electric lighting was not going as fast as the Board of Trade (HMRI) had hoped, and had the rolling stock of the train been electrically lit, the effects of the collision would have been greatly mitigated. It also recommended the installation of the GWR invention of automatic train control, a system which worked by having an insulated steel bar laid centrally between the rails at all distant signals. When a train passed over it, the bar made contact with a spring-loaded shoe and so raised it. When the lever in the signal box was at 'clear', the bar was electrified and when a train passed over it a bell was sounded in the cab because the current passed through the shoe. However, when the lever was at 'caution', the shoe remained dead and when it was raised it broke an electrical circuit in the locomotive, sounding an