 The signalling method is Track circuit Block, controlled by London Bridge signalling centre which is located nearby, adjacent to platform 16 at London Bridge station.The Thameslink train was approaching London Bridge from New Cross Gate on the Up Fast line of the Brighton Main Line, and had been signalled to cross on to the Up Passenger Loop of the South Eastern Main Line at Spa Road junction.The Connex South Eastern train was approaching Spa Road from New Cross and had received the correct signalling sequence of a Preliminary Caution (two yellow aspect signal) and Caution (single yellow aspect signal) prior to L154 (the signal protecting the junction) being at Danger.