Detectives investigating an assault on a vulnerable man near a nightclub in Hull want to trace the man in these CCTV images.
The victim, an 18-year-old man, was outside the Piper nightclub on Newland Avenue at around 1.45am on February 26 when he said something to an unknown man and woman.
Police said the unknown man took exception to his comments and went on to attack the victim along with a second man, leaving him unconscious.
The victim suffered serious facial injuries and is receiving on-going treatment at hospital.
Detective Constable Karen Smith said: “The victim in the case has learning difficulties and was attacked following innocent comments.
"Those involved carried out a sustained assault, even after the victim was knocked unconscious and ran off as the door staff from Piper came to his assistance."
Officers want to trace the man in the CCTV footage, who was wearing black clothing.
They also want to speak to anyone who was part of the man's group and the driver of the Hu30 van pictured in a third image.
It is believed the van driver could be a significant witness.
Det Con Smith said: "We would encourage the man or any of the group pictured above to get in contact with us.
"In addition we’d like to speak to anyone who can identify them or who witnessed the assault."
Anyone with information is asked to call 101, quoting crime reference number 2252504, or Crimestoppers anonymously on 0800 555 111.