Detectives investigating the murder of Dr Gary Jenkins want to speak to a potential witness.
CCTV pictures were released of a man in Cardiff city centre, who may have vital information about the assault on the 54 year-old in Bute Park.
Dr Jenkins, from Cardiff Bay, was left critically ill following the attack in the early hours of Tuesday 20th July. He died in hospital 16 days later.
South Wales Police say they're not looking for anyone else at the moment, but they believe the man seen in Cardiff could help their inquiry.
Detective Chief Inspector Stuart Wales said: ''I must stress that these people have done nothing wrong, but they may have important information that would further assist our enquiries in relation to what happened to Dr Gary Jenkins.''
''We believe the man would have been in the vicinity of the top of Queen Street, near its junction with St John Street, at around 11.30pm on Monday July 19.''
Chief Inspector Wales added: ''I would like to thank the community for the excellent support they have provided to this investigation to date, which has helped enormously.''
If you have any information in connection with the murder, contact South Wales Police on 101, quoting reference no. 254215, or Crimestoppers anonymously on 0800 555 111.
Dr Jenkins worked as a mental health psychiatrist at the Cardiff and Vale health board.
Following his death earlier this month, he was described by his family as a ''loving father, husband and brother'', who ''lived his life happily with love, music, creativity and dedication to his profession.''
Jason Edwards (25), from Riverside, Lee Strickland (36), of no fixed abode, and a 16 year-old girl who can't be named for legal reasons, are due to go on trial in January, accused of murder.