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Train services were disrupted as engineers worked to repair a damaged section of track near Dartford.
Southeastern said urgent repairs were needed after part of the track was found to be damaged this morning.
Network Rail had to close the line to repair what was described as "extensive damage" and the line was closed for a number of hours.
Trains could not run between Dartford and Slade Green or between Dartford and Barnehurst in either direction.
Due to the position of the damage, it also caused significant disruption across metro routes.
There were alterations to all services from Dartford with trains being diverted via Sidcup or cancelled.
The damage was repaired and the lines were reopened by about 11am.
Meanwhile, a fault with the signalling system at Gillingham caused further delays affecting services to London this morning.
Network Rail officers have carried out repairs but there were delays to high speed services and services towards Victoria as a result.