An armed robber fled after he was confronted by a brave passer-by who saw him targeting a couple in a Banbury park.
The offender demanded the victim's wallet after showing him a knife tucked in his waist band.
But he walked away after someone nearby saw the attack and stepped in to help.
The incident happened yesterday (Thursday June 16) in People's Park between 6.10pm and 6.20pm.
The robber walked towards the alleyway in the direction of West Bar Street.
A police spokesperson said: "An unknown male approached a couple who were sat on a bench (close to the fitness area) and demanded the victim’s wallet.
"The suspect then lifted up his top to show a knife tucked in his waist band. A witness saw this encounter from a distance and approached the couple; at this point the suspect walked towards the alleyway in the direction of West Bar Street."
The suspect is described as white, late teens - early 20s, 6ft tall, unshaven with scruffy ginger facial hair.
He wore a black unzipped hoody with the hood up, dark top underneath, black joggers and black Nike trainers with a white sole.
The spokesperson added: "Were you in the vicinity at the time and think you saw the suspect? Do you have any information which would be helpful to the Police investigation? If so, please phone 101 quoting reference 43220263974."