Resistors were placed in the traction supply of trains, to prevent a train accelerating when entering the platform, although the value of these resistors had to be changed after installation. Relays switch the resistors out when the train is permitted to leave. The system was operational in all locations by 1984. In the south-west corner of Finsbury Square, north of Moorgate station, a memorial lists those who died. Measuring , it was unveiled in July 2013 after a long campaign by relatives of the victims and supporters. On 28 February 2014 a memorial plaque was unveiled by Fiona Woolf, the Lord Mayor of London, on the side of the station building, in Moor Place. In 1977 the BBC One programme "Red Alert" examined whether an accident like Moorgate could happen again. The writer Laurence Marks, whose father died in the disaster, presented "Me, My Dad and Moorgate", a Channel 4 documentary broadcast on 4 June 2006; he stated that he believed the crash was due to suicide by Newson. In 2009 the BBC Radio 4 programme "In Living Memory" examined the causes of the crash, and in 2015 "Real Lives Reunited", aired on BBC One, recorded survivors meeting the firemen who cut them from the wreckage.