Police investigating a murder at Marsh Road, Pinner have arrested a second male.
A 31-year-old male was arrested on Friday, 29 March on suspicion of murder. He was taken to a north London police station where he remains in custody.
The 44-year-old man [A] arrested in Harrow on Wednesday, 27 March remains in custody after a warrant of further extension was granted by Willesden Magistrates Court. The warrant expires at 2235hrs on Saturday, 30 March.
A murder investigation was launched after police were called to a newsagent in Marsh Road, Pinner at approximately 06:00hrs on Sunday, 24 March.
A passer-by had found 54-year-old Ravi Katharkamar collapsed inside the shop suffering from stab injuries.
London Ambulance Service also attended but Mr Katharkamar was pronounced dead at the scene at 06:46hrs.
Formal identification took place following a post-mortem examination on 25 March at Northwick Park Mortuary. The cause of death was confirmed as a stab wound to the chest.
Detective Chief Inspector Simon Stancombe, from the Homicide and Major Crime Command, leads the investigation. He said: 'This was a vicious and unwarranted attack on a completely innocent man. Ravi's attacker got away with a few pounds worth of coins, but he leaves behind a family utterly devastated and a close-knit community asking who could do such a thing.
"The attacker fled with a shop till - have you found this discarded or seen someone in possession of a shop till who wouldn't normally have one? Do you know someone trying to use lots of loose change since Sunday morning?
"I am also keen to hear from anyone who has information about a black Vauxhall Astra that the attacker used to drive away from the scene.
"This was parked in Cecil Park prior to the murder and was drive off at speed, south down Cecil Park immediately after the attack. If you saw this car, or have seen a black Vauxhall Astra abandoned, please contact my team."
Anyone with information can also contact the incident room number on 020 8358 0200, via 101 or tweet @MetCC and quote CAD 1653/24Mar.
Alternatively, call Crimestoppers anonymously on 0800 555 111.