South West Trains say a problem at a level crossing between Barnes and Richmond means all lines will be blocked and services disrupted until around 6.30pm.
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The mother of a former altar boy who tried to blow up a train insisted he was 'a big softie' who didn't want to hurt anyone.
Its current five year licence comes to an end next Tuesday.
Extra armed police will guard major sporting events in London this weekend after the military was drafted in to protect key locations.