Two smartly dressed people could hold vital footage of a man who is suspected of carrying out a violent attack in Brighton.
A 22-year-old man was left fighting for his life after he was assaulted in Castle Square shortly before 5am on Sunday.
The suspect is a black man aged 22 to 26 who was wearing a dark hooded top and jeans at the time.
Police said he ran off through Pavilion Gardens and then was seen shortly afterwards getting into a Brighton and Hove green and white taxi and heading towards Worthing.
Officers say they have now learned that at some stage between 4am and 5am that morning the suspect was sat watching and listening to a man busking with a guitar in East Street.
The busker was performing songs requested by passers-by and was visited by two smartly dressed men who watched him play and recorded it on their mobile phones, as the suspect sat alongside the guitarist.
Police are very keen to speak to those two men and to watch the footage they recorded.
One was of mixed race, 25 to 30 and muscular. He was wearing a polo shirt.
The second was white and 25 to 35. He was wearing a blue polo shirt, possibly by Ralph Lauren.
Detective Constable Ed Downes of Sussex Police said: "Thanks to the public appeal through the media, we have traced both the man with the guitar and the taxi driver who we were looking for.
"The two people watching the busker could also be key witnesses and we are keen to speak to them as soon as possible. If you know who they are or where they could, please contact us."
Anyone who was in Castle Square next to the NatWest bank when the attack happened and who saw the incident or what happened in the minutes before or after it is asked to call Sussex Police.
They should email email@example.com quoting Operation Bunker, call 101 or contact the independent charity Crimestoppers anonymously on 0800 555111.