Disruption on Southeastern between London Bridge and Orpington, and between London Bridge and Bexley due to trespass incident between London Bridge and Hither Green.
All services subject to delays of up to 45 minutes. Some trains will be unable to run through the area until the incident is resolved.
Nearly five million passenger journeys were made on Southeastern trains during the London 2012 Paralympics.
Charles Horton, managing director said: “We carried around 100,000 extra passengers every day during the Paralympic Games, including around a million journeys on our Javelin service."
The high-speed route from St Pancras connected directly with Stratford, the station nearest the Olympic Park.
Southeastern trains between Grove Park and Bromley North have been suspended due to a broken down train. Tickets are being accepted on local bus routes.