A woman was killed by a falling tree branch in Kew Gardens during rain and gusts of wind close to 30mph, police said.
The woman, believed to be around 30 years old, was pronounced dead at the scene yesterday afternoon, on a day when strong winds and rain lashed the country, Scotland Yard said.
Wind speeds in the area around the Royal Botanical Gardens at Kew, south-west London, reached a peak of 30mph at 4pm yesterday and were likely to be close to that at the time of the woman's death, Tom Tobler, forecaster with MeteoGroup, the weather division of the Press Association, said.
Her death came as communities around the country braced themselves for wind speeds of up to 70mph and rainfall of up to 60mm in some regions over the next 24 hours. The Environment Agency issued has 56 flood alerts - 31 in the south-west, 19 in the north-east and six in the Midlands.
Mr Tobler said north-east Scotland could be hit with the strongest winds, with gales of up to 70mph possible.
He said northern areas of England and parts of southern Scotland could see 60mm of rain fall in the next 24 hours - three quarters of a whole month's average rainfall (80mm) for September in England and Wales.
The forecaster said: "It's almost a month's rainfall in certain areas. It is certainly a lot of rain.
"There will be some flooding. I imagine the figure for total rainfall in the month will get up to the average tomorrow, if not above the average figure."
It is a stark change from earlier in the month, when parts of Britain basked in warm temperatures in the mid-20s, a welcome break from the rain and wind which dogged much of July and August.
Last night, the Environment Agency warned people to be prepared for significant disruption.
Its director of operations, David Jordan, said: "We are expecting flooding across the country from this evening (Sunday) and in to Monday and Tuesday.
"We strongly urge people to sign up to flood warnings, keep a close eye on local weather forecasts and be prepared for the possibility of flooding. We also ask that people stay safe, by staying away from swollen rivers and not attempting to drive through floodwater."
The woman's death at Kew is not being treated as suspicious and a police spokesman could not confirm whether the matter would be referred to the Health and Safety Executive (HSE).
An air ambulance was sent to the scene and extensive efforts were made to revive the woman, a London Ambulance Service spokesman said.
"We were called just before 2.05pm to reports that a large tree branch had fallen on a woman in Kew Gardens," he said.
"We sent an ambulance crew, three responders in cars, an officer and London's Air Ambulance to the scene.
"Extensive efforts were made to resuscitate the patient, but sadly she was pronounced dead at the scene."