The body of a man, believed to be in his early 20s, was recovered from the Thames near Hampton Court last night.

Large numbers of people have been swimming in the river during the heatwave in an attempt to cool off.

The biggest risk is linked to people jumping into the river from foot and road bridges across the Thames where cold water shock can lead to virtual instant drowning.

Last month a boy aged 14 – Brian Sasu, who was a pupil at St Marks Catholic Secondary - died in a drowning after apparently jumping from a bridge near Taggs Island at Hampton.

Richmond Council Leader, Gareth Roberts, said today: "Absolutely heart breaking that almost a month to the day after Brian Sasu lost his life at Taggs Island, there has been another tragedy in the river, just a little further along at Hampton Court.

"Please, if you have young family or work with young people warn them of the danger."

There is no evidence that the man who died on Sunday afternoon had jumped into the river. Eye-witnesses suggested he had been standing in waist-deep water before suddenly disappearing.

The Metropolitan Police said a multi-agency response was launched following a call to a person in the water at Hampton Court at 4.12 pm on Sunday.

They said: "Officers from the South West Command Unit and Surrey Police, the National Police Air Service, as well as the London Fire Brigade, London Ambulance Service and RNLI, began searching the river.

"At around 10.30pm the body of the man - believed to be aged in his early 20s - was recovered from the water by police divers.

"His next of kin have been informed."

Eyewitnesses said that a man in his 'mid- to late-teens' was swimming in the River Thames when he got into difficulty.

Max Taylor, a senior news editor at NBC, was paddle-boarding at Hampton Court Palace when the incident happened, and spoke to eyewitnesses.

"They told me a young male in his mid-late teens was swimming in the river near Hampton Court bridge,'"he told Sky News.

'He called for help and was in waist deep water. They said they thought he was joking as he wasn't in deep water — seconds later he had disappeared.

'I paddled past and saw the inflatable search boats go in and start looking for the young lad."