Southern Rail said a communications alarm was activated on the 2pm London Victoria to Brighton service whilst the train was leaving Gatwick Airport. The alarm resulted in the train having to stop whilst the driver investigated the incident. Southern said the stoppage caused the line between Gatwick Airport and Three Bridges to become blocked causing delays of up to 15 minutes on services travelling to Horsham and Brighton. Gatwick Airport is also undergoing planned engineering work which has added to further disruption, Southern added. A spokesman said: “As a result of this and one of the lines being blocked, some congestion and delays have built up through the station. As train carriages and crew will not be in the correct places to start their next journeys on time, it may take some time for train services to return to normal.” Delays are expected to continue until 5pm this evening.