Thames Water has announced a hosepipe ban for all its customers.
The restrictions mean hosepipes should not be used for watering gardens or allotments, cleaning cars, filling paddling pools or swimming pools, or cleaning windows.
The water company cited the UK's "exceptionally warm and dry spring", with the region having 40% of average rainfall and more days at or above 34C this year than ever recorded before.
Nevil Muncaster, director of strategic water resources, said: "We would not be taking this step unless it was necessary to protect water supplies for everyone and the environment."
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