A former chief constable of Merseyside Police broke off from a radio interview to make an arrest today.
Metropolitan Police Commissioner Sir Bernard Hogan-Howe jumped into a taxi to pursue a suspect after the driver complained his passengers refused to pay the fare and had stolen cash from him, the BBC reported.
He had been talking to BBC London 94.9 near Bruce Grove station in Tottenham, north London, at the time of the incident.
Sir Bernard later apprehended a teenager, Scotland Yard said.
His force said in a tweet: "Commissioner Hogan-Howe arrested a 19yo man on suspicion of theft this morning after being flagged down by local taxi driver."
The driver, who gave his name as Mohammed, told the BBC a passenger took £20 from his dashboard before running away.
He said: "When I see the police, I ask the police 'please can you stop the guys?"
He said he was not aware who the officer who came to his aid was, but described him as a "very good, very kind" man.
It is not the first time Sir Bernard has gone back to his "bobby" roots.
In 2006, when he was chief constable of Merseyside Police, he chased and arrested a suspected drink driver in Liverpool.