The Evening Standard is reporting that Radcliffe was part of a group of people who came over to help a tourist after a robbery.
Two men on a moped targeted the man, stealing his Louis Vuitton bag and leaving him with a facial injury, according to witnesses.
"He was a really nice bloke, a lot of stars wouldn't have stopped to help. I'm still on the phone to the police", he said, before they struck out. He wasn't going to give up the bag willingly.
Former police detective David Videcette was on the scene, providing his account of the suspicious moped drivers and the aftermath, saying, "The victim was very, very shaken up".
The victim - who was only in the United Kingdom for a short holiday - had been targeted for his Louis Vuitton bag, which the muggers made off with after cutting his face with a knife.
Ex-cop David Videcette told the Evening Standard he followed the moped muggers, even shunting their bike with his vehicle before they sped off.
A spokesperson for Radcliffe confirmed he was present but declined to comment further. The victim was walking when two men on a moped approached him, stole his Luis Vuitton bag and fled the scene.
A spokesman for the Met Police said: "Police were called at approximately 6.10pm on Friday, July 14 to reports of a robbery in Hortensia Road".
The Met Police said there had been no arrests as yet, and officers from Kensington and Chelsea were investigating.