The Clayton Tunnel rail crash occurred on Sunday 25 August 1861, five miles (8 km) from Brighton on the south coast of England.

The signaller at the south end of the tunnel belatedly waved a red flag in an attempt to stop the second train, but thought that it had not been seen.

[1] In his cabin close to the southern entrance of the tunnel, signalman Henry Killick was in charge of a signal linked to an alarm bell, and a needle telegraph.

Except for the Clayton Tunnel, the line was worked on the time-interval system, which required trains on the same track to be separated by five minutes.

It concluded with the jury finding that Charles Legg, the assistant stationmaster of Brighton station, was guilty of manslaughter, because of his negligence in starting three trains so close together, against the rules of the company.

[3] The catastrophe publicised the problem of trains travelling too close together, with signalmen having to appraise the situation too quickly for safety's sake.

A simple communication mistake between the two signal boxes caused havoc that Sunday, but the telegraph was also blamed for the tragedy because it did not register without continual pressure on the switch.

In his report on the accident Captain Tyler stated that "it was disgraceful that a man in so responsible a position as Signalman Killick should be compelled to work for twenty-four hours at a stretch in order to earn one day of rest a week.

"[4] Charles Dickens may have partly based his story "The Signal-Man" on this accident,[5] dramatising the events (especially the bells and the telegraph needle), as well as adding other incidents.