The 25-year-old was making his way home along Warple Way at the junction of Valetta Road, Acton, just after 6pm, when he was approached and surrounded by four black youths in their mid-to-late teens.
They aggressively demanded his mobile, assaulted him and then stabbed him in the chest before running off down Valetta Road towards Larden Road.
One man who was working late said he was ready to leave at 8.45pm but the police stopped him from going to his car as it was parked within the cordoned off area.
He said: "I was just leaving and noticed around five or six police officers on the other side of the road. I saw a bike leaning against the wall and a man sitting on the pavement. I thought maybe he was drunk or asleep but was told he had been stabbed and I could not leave until the police got all the evidence they needed and finished investigating the area. They also said it appeared to be a mugging which got out of control and at first, they thought the stab
wound might be life threatening." Less than an hour later, at 6.50pm, a 58-year-old man was approached by four black youths and stabbed at the top of his left leg and back of his right hand as he was making his way home along Kingswood Road, near South Acton British Rail Station.
The teenagers ran off down Cunnington Road towards Acton Green and could possibly have been joined by more youths, including girls.
Both the victims were treated in hospital and are now recovering at home.
Anyone with information on either attack is asked to call Acton CID on 020 8721 7101.
