A dog walker captured on CCTV footage is being sought by police investigating the murder of a man exactly a year ago.
The body of Scott Wilkinson, 48, was pulled from the river in Walton-on-Thames, Surrey, on 28 July 2016, a short distance from "Donkey Island".
Police believe he was killed on the island near Sunbury Lock where he had been fishing the evening before.
Det Ch Insp Paddy Mayers said the person sought was not believed to have had any involvement in the murder.
The dog walker was seen on CCTV just after 08:00 BST on 28 July, around the same time Mr Wilkinson was reported missing.
"That person may well have significant information to assist us," Det Ch Insp Mayers said.
He urged anyone who recognised the dog walker, or who was on the island prior to the murder and had not yet spoken to police, to come forward.
"Scott, a son, brother, father and grandfather, was dearly loved by all who knew him and we will leave no stone unturned to get justice for Scott and his family who are still, one year on, coming to terms with his death," he added.
A post-mortem examination found Mr Wilkinson died from head trauma.