David Beckham bought hot drinks for a paramedic and her patient after he spotted them waiting for an ambulance in the cold.
Cycle response paramedic Catherine Maynard was helping an elderly man, who had fallen in central London.
Ms Maynard said the former England captain greeted them, got in his car and returned 10 minutes later with cups of tea and coffee.
"We were both very amused and flattered," she said.
'Think that was Beckham'
Ms Maynard said she had been trying to keep her patient warm as they waited for an ambulance near Endsleigh Street.
"All of a sudden, I looked up and saw someone who looked like David Beckham walking past us," she said.
"He said hello and got in his car. I said to the man I was treating, 'I think that was David Beckham'. Ten minutes later, he came back with a cup of coffee for me and a tea for the patient.
"It was awful cycling around in the cold today and I couldn't believe it when he came back with some hot drinks - I was so chuffed."
London Ambulance Service said Beckham had shown he "respects hard-working paramedics and even a gesture as small as buying a cup of coffee makes our crews feel appreciated".
The patient was taken to hospital where he was treated for minor injuries.