A man was stabbed in front of a queue of people waiting to buy the latest edition of a computer game.
Up to 100 people witnessed the knife attack outside the Gamestation store in Croydon, ahead of Monday's midnight release of Grand Theft Auto IV.
Police said the 23-year-old victim was walking past the queue when he was stabbed several times by a hooded man who appeared to be waiting in line.
The victim was treated in hospital and has since been allowed home.
After the attack at about 2300 BST in George Street the victim did not call the emergency services but police were informed by a member of the public.
He was found not far from the store and taken to hospital where he was treated for several stab wounds.
Det Insp Liz Baker urged anyone who was in the queue to contact them.
She said: "We are looking at CCTV from the area and believe there were in the region of 50 to 100 people in the queue.
"We are sure many of them will have seen what happened."
The suspect is described as being a light skinned black man aged about 21, 6ft 5ins tall, of medium build wearing a light grey hooded top.
Grand Theft Auto IV went on sale at midnight at selected shops in the UK.
It was expected to break records for the fastest-selling game of all time .