Police are appealing for witnesses after an off-duty officer was stabbed when he tried to stop a robbery in south London.
The 37-year-old saw four men on mopeds trying to steal another moped shortly before 6pm on Saturday.
According to Scotland Yard, the suspects were armed with a large kitchen knife.
The officer, who has not been named, challenged the group, who were targeting a 21-year-old in Lewisham.
He was stabbed in the leg, but refused to back down and the moped gang eventually fled empty handed.
The 21-year-old victim was left with bruises but his injuries are not life threatening.
Lewisham Police are trying to identify those responsible.
A spokesperson said: “Officers are keen to hear from anyone who either witnessed the incident or has information that could assist the investigation.”
:: Anyone with information is asked to call Lewisham Police on 101, quoting reference CAD5786/11AUG, or call Crimestoppers, anonymously, on 0800 555 111. Alternatively, witnesses can tweet @MetCC.