There are widespread delays around Waterloo station after police handled a trespass incident near the railway.
Disruption is expected until the end of the day.
South Western Railway warned: “Trains may be cancelled, delayed or revised because of this problem.”
Meanwhile motorists on the M25 are facing delays of around an hour following a crash.
National Highways warned drivers should expect around eight miles of congestion on the clockwise carriageway at Junction 27, near Epping, where the outside lane is closed due to the collision.
The Metropolitan line and Piccadilly line were part-suspended on Friday afternoon but have now reopened.
Minor delays remain on the Central and Piccadilly lines.
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