A man has been arrested on suspicion of murder after a passenger was found stabbed to death on a bus in central London.
The 38-year-old was arrested on Saturday, accused of killing Archie Sheppard, 48.
Mr Sheppard, from Neasden, north-west London, was discovered on the top deck of a Route 189 bus on Friday.
Police and paramedics were called to the bus in Gloucester Place, Marylebone, at 00:10 BST.
Mr Sheppard was pronounced dead at the scene following a "violent and sustained attack".
Saturday's arrest took place in Mulgrave Road, Fulham, south-west London.
The suspect was also detained on suspicion of possession of an offensive weapon, after being found with a knife.
Scotland Yard appealed for help in searching for a white male seen with Mr Sheppard shortly before he boarded the bus in Brent Cross, north London, at 23:13 on Thursday.
The attacker is believed to have fled the bus as it reached Gloucester Place and the junction with Montagu Place, heading in the direction of Marble Arch, police said.
Det Ch Insp Noel McHugh said: "Whilst we have made an arrest, this is just the beginning for my investigation.
"We are now appealing to those who knew Archie Sheppard in whatever capacity to come forward.
"It is important that we establish and get a clearer picture as to who Mr Sheppard was and the lifestyle he was leading, in particular anyone who was with him on Thursday 27 April, and anyone who stayed at his home in Neasden.
"I am also making a fresh appeal for information and witnesses to come forward.
"There are still a number of witnesses that have yet to come forward and I believe they could hold vital information that could help with progressing this investigation."