National Rail Enquiries says that the disruption is likely to last until at least 10pm.
Passengers are being allowed to use their tickets on buses between London Bridge and East Croydon, Purley and Caterham, on London Overground and London Underground services on 'reasonable routes' and the Tramlink between Beckenham Junction and East Croydon.
We apologise for disruption again tonight. If any minor consolation, we hope at least your experience on the station was improved tonight.
Commuters are facing a fourth night of disruption at London Bridge station. Signalling problems are a causing delays to all Southern services using the station.
There were delays of up to 45 minutes due to a signalling problem.Read the full story ›
All platforms are now open at #LondonBridge following a security alert. Delays of up to 40 minutes and alterations expected until 2130.
Passengers at London Bridge station have reported being evacuated by armed police. According to the Met Police, officers were called after reports of a man on a train making threats.
4 armed response police with big guns just ran past me at London Bridge station. Incident platforms 1 to 6.
Eek, there's a guy at London Bridge station making threats.. they've evacuated the station... police swarming. Be safe, kids!