Detectives released a second CCTV image of a suspect wanted over random assaults on two men in Covent Garden.
One victim – in his 70s – was left with serious injuries and an off-duty police officer punched in the back of the head close to the Royal Opera House.
Both attacks occurred within moments of each other at around 10.30pm on October 12 in central London, the Metropolitan Police said.
The officer, attached to Central East Command Unit, was not injured.
But his assailant then approached a pensioner in nearby King Street initially asking for directions, before pushing him over.
He suffered a bleed on his brain and temporarily lost consciousness.
The victim required 15 stitches and is no longer in hospital but continues to suffer the effects.
Neither victims is known to each other and the assaults appear to have been random, with no known motive.
The Royal Opera House in in Covent Garden (PA)
The suspect is described as white, around 5ft 9in tall, of medium build, and wearing a black jacket. He was last seen fleeing towards Bedford Street.
Police have made a renewed appeal for information and released a new CCTV image of the suspect. It shows him earlier wearing the exact clothing he had on at the time.
There has been no arrest and enquiries are ongoing.
Detective Constable Greg Atkins, from the Met’s Central West Command Unit, said: “This incident took place in and around Covent Garden on a busy evening.
“We are making a renewed appeal for anybody with information to come forward. Do you recognise the suspect featured in the CCTV images?
“Multiple people witnessed the assaults and I would ask anyone who can assist in identifying the person responsible to get in contact.”
Anyone with information that could assist should call police via 101, quoting CAD reference 7846/12OCT, or the independent charity Crimestoppers on 0800 555 111.