Disruption on South West Trains between London Waterloo and Barnes, and between London Waterloo and Wimbledon due to signalling problem.
All trains to and from Waterloo are at a stand-still at the moment.
More top news
Over 40,000 people picked up their packs to take part in the annual marathon in the capital.
The boyfriend of reality TV star Ferne McCann has been arrested on suspicion of attempted murder following an alleged nightclub acid attack.
At least 100 firefighters are battling a huge warehouse fire in Essex.