Power cuts struck parts of central London today as high temperatures prompted soaring demand.
EDF Energy said four unrelated faults sparked a problem with its power distribution.
Four-hour shutdowns will affect hundreds of the energy giant's customers today and possibly tomorrow.
Some 760 customers are currently without power. Shutdowns are likely to hit two other groups of 1,200 and 1,300 more customers later today.
The power problems led to the closure of Oxford Circus Tube station, one of the busiest in London, for almost an hour and a half at lunchtime today.
London Underground said the station experienced power problems from 10am when lighting was affected and it closed just before 1pm.
It later reopened after a generator was brought in to provide additional power.
An LU spokesman said the company was working with EDF and hoped there would be no further closures.
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