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.