A murder investigation has been launched after a man assaulted in a "mindless" attack in Trafalgar Square more than six months ago died in hospital.
Desmond O'Beirne never recovered after suffering a devastating head injury when he was kicked and punched by two men outside the National Gallery in the early hours of June 3.
The 51-year-old, from Westminster, was taken to hospital and died from his injuries on December 20.
Detectives have called for the public's help in tracing Mr O'Beirne's attackers and have called on anyone who witnessed the attack, or events either side of it, to come come forward with information, mobile phone images or footage.
DCI Noel McHugh from the Metropolitan Police's major crime command, said: "These two men will have spoken to friends and partners and possibly boasted about their mindless attack. I want you to call us with their names.
"The males are distinctive and will be known to their group that evening. Desmond never regained consciousness after the brutal attack and it is vital we bring his attackers to justice."
The attack at around 12.25am was caught on CCTV footage which shows one bearded suspect punching Mr O'Beirne on the back of the head. The second suspect then kicks Mr O'Beirne as he lies collapsed on on the pavement.
Scotland Yard said the first suspect had his hair in a "top knot" style and was wearing a red t-shirt, dark trousers and light coloured shoes.
The second man was wearing a black jacket with a white emblem on right shoulder and white writing with a picture on the rear. He was also wearing a white top under the jacket, dark trousers and dark shoes with white soles. Anyone with information is asked to contact the incident room on 020 8785 8099. To give information anonymously they can call Crimestoppers on 0800 555 111 or visit crimestoppers-uk.org. They can also tweet information via @MetCC.