On the morning of 1 September 1905, a train left London Liverpool Street, bound for Cromer. As it approached Witham railway station, disaster struck.
Most of its 14 carriages left the tracks, sliding up the platform on their sides, even overturning completely.
Eleven people - including a 10-year-old girl - lost their lives in the crash, with more than 70 injured.
But further catastrophe was just moments away as another train approached at speed, heading for the wreckage.
The quick reactions of a signalman and his colleagues prevented even greater loss of life.
More than a century later, their brave actions - and the lives lost on that day - will be commemorated for the first time.