The Jubilee line was hit by severe delays during Tuesday's morning rush hour because of a signal failure.
The signal failure, between Finchley Road and Waterloo, caused huge disruption on the entire line.
Services resumed between the two stations just before 7.30am, but Transport for London (TfL) warned: "Jubilee line train services between Finchley Road and Waterloo are running again with severe delays on the entire line."
TfL "strongly advised" people to use alternative routes where possible.
The disruption later cleared at about 8am, with TfL saying there were minor delays between Willesden Green and Baker Street.
A TfL spokesman said: “We apologise to customers on the Jubilee line who had their journeys disrupted this morning.
"This was due to a fault with the signalling system, which our engineers worked to fix as quickly as possible.”
The Jubilee line runs from Stanmore, north-west London, to Stratford, east London. It serves 27 stations.
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