Metropolitan Police Commissioner Sir Bernard Hogan-Howe jumped into a taxi to pursue a suspect after the driver complained his passengers had refused to pay the fare and stolen cash from him.
Sir Bernard, who was taking part in a pre-recorded interview with BBC London 94.9 Drivetime presenter Eddie Nestor near Bruce Grove station in Tottenham, north London, joined the chase first in the minicab and later in a squad car.
He went on to apprehend a teenager, Scotland Yard said.
The driver, who gave his name as Mohammed, said he was not aware of the identity of the officer who came to his aid, 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.
It means Sir Bernard has made an arrest in every rank he has held since becoming an officer in 1979, Scotland Yard said.