Rail commuters using on one of London's busiest lines were forced to exit the train this morning and walk along the track.
Further overhead wire problems were found on the East Coast Main Line in Hertfordshire which meant trains were unable to run between Stevenage and Hitchin.
Train companies were hoping to put buses on to operate between Letchworth/Biggleswade and Stevenage.
The continuing problem, which had led to hours-long delays to evening rush-hour commuters yesterday, affected passengers with four train companies - East Coast, First Capital Connect, First Hull Trains and Grand Central.
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Want to know its posh name? It's a 'Track Retrieval Device'.
Unite said its members in the capital's 18 bus operators had supported walkouts by 85%, and action short of a strike by 9-1.