She returned to her home, but as she went to knock on a neighbour’s front door to verify who the men were, the first man grabbed her handbag and an envelope containing the money.
He and the other two suspects, both white and believed to be aged about 25 and 65, then made their getaway in the vehicle.
Detective Constable Steph Barron, of the Camden Major Crime Unit, said: “This is a heinous crime perpetrated by three callous and heartless men on a vulnerable member of our society.
“I suspect that this is not a one-off fraud committed by these men, so I am eager to hear from other victims. This will help me to find them and lock them up.”
Police have so far made no arrests in connection with the incident.