Police were called to Belmont Circle, in Kenton Lane, Harrow, at 1.15am on April 7 to reports that a man had been injured .
Metropolitan Police and London Ambulance Service attended.
A man, aged in his 40s, was taken to hospital for treatment by the London Ambulance Service.
He remains in a critical condition and his next of kin continue to be supported by specialist officers, Scotland Yard said.
Following initial enquiries three men have been arrested and charged.
Justin Robson, 19, of Long Elms, Harrow, was arrested on April 10 and charged the following day.
He will next appear at Harrow Crown Court on May 9.
Owen Vandersluys-Bodman, 25 of Manor Way, Ruislip, and James Dawson, 22, of Whittlesea Road, Harrow, were arrested on April 12.
Both were charged on Saturday, April 13.
They will next appear at the Old Bailey on May 13.
A woman who was arrested on suspicion of assisting an offender, has been released on police bail to a date in May.