Later on, some LNER trains were running southbound into King's Cross, and services to Stevenage and Peterborough from London also resumed, but not further up the East Coast Main Line. Striking during rush hour, the blackout left commuters stranded in the city.
It also affected road travel, with traffic lights not working on London streets.
Large parts of England were without electricity following a large scale power cut causing transport disruption including trains travelling to and from Edinburgh breaking down.
A hospital in the town of Ipswich said its back-up generator had failed.
She said other generators "kicked in as was required" and "patients were kept safe and cared for throughout".
"We believe this is due to a failure on National Grid's network, which is affecting our customers".
The power was restored around 6:30 p.m. (1930 GMT) and "the system is now operating normally", it said.More news: Palestinians and Israeli police clash at Jerusalem holy site
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He said that there was "no indication" that the power cut was due to a lack of investment in major infrastructure.
The power failure came as heavy rainstorms drenched the London area, causing flooding at Luton Airport, about 47 kilometres north of the capital.
He explained that the two power stations disconnected from the grid "near simultaneously".
A spokeswoman for Northern Powergrid said 110,000 of its customers lost power between around 5.10pm and 6pm.
He said: "We urgently need answers from the government over this fiasco".
The airport said in a statement that the "unprecedented rainfall" had caused "water damage in a number of locations in the terminal" and apologized for the disruption.
"All trains were stopped while our back-up signalling system started up".
Western Power Distribution shared a similar message, and said they are in the process of restoring power to customers.
"People whose journey was severely disrupted should also keep receipts for all unexpected costs that arose from their efforts to complete their journeys yesterday, and contact their train operator to claim not just for their delay but any additional expenses they incurred".