Tens of thousands of South West Trains passengers are tonight caught up in major disruption with long delays and cancellations to services from Waterloo to the south.
Passengers say conditions in the hot weather are unbearable.
A series of signal and track failures have led to massive delays.
The problem is expected to last until the end of service.
Thousands of rugby fans are at Waterloo making the trip to the Twickenham opening of the World Cup. The station is on the line to Windsor and Reading.
Regular passengers were asked to consider changing travel during the rush hour to avoid crowding.
While Waterloo is extremely busy, services and the flow of passengers is working well.
Many appear to have heeded the travel advice.
Commuters hit by long delays on South West Trains services into London Waterloo this morning have been re-acting to a tweet thanking them for their patience.
Long delays are expected until lunchtime due to signalling problems between Wimbledon and London Waterloo.
Commuters in the Thames Valley have been warned they will have to deal with disruption for several hours during the morning rush after a signalling problem on a busy railway line into London.
Passengers could be delayed by up to an hour as a result of a problem between Wimbledon and Earlsfield which sparked cancellations on services into and out of Waterloo.