Detectives investigating an attack on three university students in Sheffield want to trace a witness who recorded it on a mobile phone.
A number of people witnessed the incident near to the Kebabish takeaway on London Road, with police understanding that one man captured the attack on his phone.
Three PhD students were attacked by two men and two women at around 2am on Sunday, June 22.
One of the victims, a 25-year-old woman, was pulled to the ground by her hair and suffered minor bruising and grazing.
Her partner, a 31-year-old man, was punched in the face and suffered serious eye injuries which require surgery.
Their friend, a 26-year-old man, suffered minor bruising to his head and throat after being grabbed around his neck.
PC Richard Gay, who is investigating the incident, said: “All four played a part in the assaults, which were totally unprovoked.
“There were several people who will have witnessed this attack and, in particular, one person who actually recorded it on his mobile phone.
“Unfortunately he did not leave his details with the victims, and we are now urgently seeking to trace him.
“We also want to speak to anybody else who may have witnessed this vicious assault on a group of defenceless young people.”
Anybody with information about the incident should call South Yorkshire Police on 101, quoting incident number 195 of June 22.
Crimestoppers can also be contacted anonymously on 0800 555 111.