Detectives have released a CCTV image of a man they want to speak to after a teenager was assaulted before his attackers tried to stab him in a fast food restaurant.
Police said three men punched the victim to the ground before kicking him after a "verbal altercation" in Rye Lane, Peckham.
The victim, 19, was able to get to his feet and run into a fast-food restaurant but was pursued by two of the men.
One of them then produced a knife and tried to stab him several times before the two attackers fled the scene, police said.
The victim received a cut to his hand and was later treated in hospital for the wounds he sustained in the attack, at around 3.15pm on April 22.
A 21-year-old man was arrested on suspicion of grievous bodily harm with intent and has been bailed to a date in late July. Scotland Yard said another male remains in police custody.
Police said the third suspect, shown in the CCTV image holding a knife remains, unidentified.
He is described as light skinned black male with long, braided hair, of slim build and approximately 6ft tall. He was wearing a grey sweatshirt with the words 'Sneaker Freak' on the front and blue jeans.
Anyone with information is asked to contact DC Tessa Lyle-Meller of Southwark CID on 101 or call Crimestoppers anonymously on 0800 555 111 quoting reference 3011268/15.
