A fire at an EDF Energy substation at the Elephant & Castle is thought to have been the cause of a power failure across north Southwark on Tuesday afternoon.
Southwark Council says that power supplies were isolated for safety reasons shortly after 2pm.
Power supplies were restored to the majority of affected customers by around 4pm, and by 5.30pm some 400 properties were still without power.
Train services at London Bridge Station continued to operate but passenger information screens and loudspeaker systems were not working.
Local arts radio station Resonance FM, which has its studios in Borough High Street and transmits from Guy's Tower, was also taken off the air.
At one stage parts of Borough High Street had power restored whilst the Post Office at London Bridge remained in darkness.
Enrolment of new students at London South Bank University was also affected by the power cut.
At 7.30pm the Rockingham Estate was still without power.