A 44-year-old man has been arrested on suspicion of the murder of 87-year-old Thomas O'Halloran on a mobility scooter in west London.
He was arrested at an address in Southall, West London, in the early hours of Thursday, the Metropolitan Police said.
Detective Chief Inspector Jim Eastwood, who leads the investigation, said: "I would like to thank the public for their overwhelming support following this horrific incident. As a result of the release of a CCTV image yesterday, an arrest has been made and this investigation is progressing at pace.
"Mr O'Halloran's family have been updated with this development and continue to be supported by specially trained officers."
On Tuesday afternoon, 87-year-old Thomas O'Halloran was stabbed to death on his way home, managing to travel around 75 yards on his mobility scooter, shouting desperately for assistance, before succumbing to his wounds.
Mr O'Halloran was attacked near Greenford's Cayton Road, just off the A40, at around 4pm by at least one knifeman, who police described as extremely dangerous
Neighbours rushed to help and tried administering first aid before paramedics arrived.
Mr O'Halloran was declared dead at the scene, with his attacker having already disappeared, either into the surrounding streets or an underpass beneath the A40 Western Avenue.
Footage from the scene posted online showed paramedics running to treat the victim.
Mr O'Halloran's murder, the 59th in the capital so far this year, left those who knew him stunned.
Hitesh Patel, 62, a shop owner at Greenford station, told The Telegraph that Mr O'Halloran, who he said had three children, would often play the accordion on his mobility scooter outside Tesco and Greenford station to raise money for Ukraine victims.
Mr Patel said: "He was Irish and he had a white beard and he used to play music outside.
"People used to call him Mr Bond because he would drive around on his scooter and rev the engine.
"He has lived here a long time. Maybe 20 years. I know his wife as well. He had quite a few sons I think.
"Every day he would come and play here. We knew it was him because he had a Ukraine flag on his scooter and he used to raise money for charity."
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