Passengers on some of the busiest rail routes in London were warned of cancellations because of over-running engineering works.
No South Western Railway trains were running between Surbiton and London Waterloo - the UK's busiest railway station.
It is the latest disruption to hit SWR following a spate of problems involving signal and points failures.
A long-running dispute over the role of guards on trains has also crippled services because of strikes.
A message to passengers said:
Normally-packed commuter trains were cancelled, leaving tens of thousands of passengers stranded.
Southern services between East Croydon and London Victoria were also disrupted because of over-running engineering works.