Detectives are appealing for information after a 79-year-old man was left with a substantial laceration to his head and a fractured hip following an attack on New Year's Eve in Archway.
They have issued CCTV footage and stills of a man they would like to trace in connection with the incident.
Police were called by the London Ambulance Service at approximately 14:50hrs on 31 December 2017 to reports of an altercation in Highgate Hill.
The victim and the suspect had been in the McDonalds restaurant near to Archway Underground Station and there was a brief exchange of words between them prior to the suspect leaving.
He left and walked towards Holloway Road and the victim left in the same direction a short time later.
Approximately two metres from the exit of the restaurant the suspect turned around and approached the victim.
The victim was punched in the face by the suspect causing him to fall to the ground.
The suspect made off in the direction of Holloway Road and Archway Underground Station.
The victim was taken to hospital by the London Ambulance Service after suffering a deep laceration across his forehead and a fractured hip.
The suspect is described as a white man, of average build, aged between 30 and 40 years old. He has short dark hair with a receding hairline.
Detective Constable Darren Burt, of the Central North Command Unit, said: "This appears to have been a completely unprovoked attack on an innocent man, whose life may now be changed forever due to his injuries.
"Over a month later, the victim is still in hospital following hip surgery. We urge anyone who recognises this man or has any information to come forward and contact police."
Anyone with information should contact police on 101 quoting CAD 4091/31 December. Alternatively, contact Crimestoppers anonymously on 0800 555 111 or online at crimestoppers-uk.org