A Tesco shopper was stabbed with a Swiss army knife after getting into an argument with a fellow customer at a branch of the supermarket chain in northeast London.
The Metropolitan Police has released an image of a man they want to speak to in relation to the attack on Francis Road, Waltham Forest, on 14 July.
The victim, a 39-year-old man, was taken to hospital for treatment.
His injuries were described as not life-threatening but he was "incredibly shaken" by his ordeal.
Police said the victim visited a Tesco Express store on Leytonstone High Road at around 5.03pm.
He got into an argument with the assailant outside the shop.
The victim was then followed by the assailant onto Francis Road, a short walk away, where he was stabbed.
The suspect is believed to have used a Swiss army knife.
Detective Constable Alexandra Varga is investigating. She said: "We know the images are not the best quality, however we hope members of the public will study them carefully and contact.
"This was a sudden and utterly unnecessary escalation of violence and we must identify the person. Please don't hesitate if you have information that could help."
Call 101 or tweet @MetCC ref CAD 5895/14 Jul.
To remain 100 per cent anonymous contact the independent charity Crimestoppers on 0800 555 111.
There have been a number of knife attacks in the capital in recent weeks.
An 87-year-old grandfather on a mobility scooter was stabbed in west London on Tuesday. A 44-year-old man was arrested on suspicion of murder on Thursday.