A mobile phone image has been released showing three men who are wanted for questioning after two friends were stabbed and beaten outside a pub.
David Sayer (middle) was pictured with three men in the background
David Sayer and Mario Smith were attacked in Lordship Lane, Tottenham, north London, in March after helping the landlord eject three men.
Earlier that evening another friend took a photo of Mr Sayer, which caught the suspects in the background.
Police say the three are wanted in connection with attempted murder.
Mr Sayer, 38, was stabbed five times in the back, side and stomach, but managed to stumble back into the New Moon pub just after midnight on 12 March.
Mr Smith, 29, was stabbed three times in the back, hit with a baseball bat and kicked in the head after he fell to the floor.
Three men were told to leave the pub
Both needed emergency life-saving treatment - Mr Sayer had to have part of his bowel and spleen removed.
Det Sgt Alan Dawson, from Haringey CID, said: "This was a brutal attack where both men are lucky to be alive. We are determined to catch the violent men that are responsible."
He said CCTV footage was not good enough to identify the attackers and they have hit a dead end trying to identify them through local inquiries.
"On the evening a friend of the victim took a camera photograph of him whilst he was sitting in the pub," said Det Sgt Dawson.
"She has also managed to capture three men in the background of this picture who we are eager to question about the attack.
"We are hopeful that someone must know their identities."
The victims had been enjoying a family party with friends at the pub that night and stepped in to help when the landlord asked three men to leave because he was unhappy with their behaviour, police said.
They said the attack was unprovoked and are offering a £20,000 reward for information leading to a prosecution.
Mr Sayer and Mr Smith are both now out of hospital and said to be slowly recovering from their injuries.