Rail services to one of the key Olympic stations were delayed on Wednesday morning, while there were also hold-ups at another major London terminus.
Some passengers were stuck for around 30 minutes outside London Bridge station due to "operating problems".
The difficulty led to delays to services run by the Southern train company in and out of London Bridge in the morning rush-hour. A spokesman for Southern Railway said the delays were caused when a train was signalled into the wrong platform at the station. The 10-carriage train arrived at a platform intended for trains with eight carriages.
The spokesman said: "It meant the train had to be sent back along the track, which caused congestion."
Passengers faced delays of about 20 minutes before services returned to normal at 8.30am.
London Bridge is one of the major Olympic hub stations, dealing not only with arriving commuters in the morning but those leaving to go to Olympic events.
There were also problems at Cannon Street station where a signalling problem meant fewer trains to and from this main London terminus. This affected services run by the Southeastern train company.
There were also travel difficulties on the Tube, with a signal failure at Turnham Green in west London resulting in no District line services between Earls Court and Richmond/Ealing Broadway.
The problem at Cannon Street persisted through the day. It was announced that some Southeastern services would leave from Victoria station tonight rather than from Cannon Street.
The Association of Train Operating Companies and Network Rail said train companies provided more than 574,000 extra seats, operating more than 4.2 million seats in total.