Have-a-go hero Steven Broadbent, 30, from Mirfield, rammed a getaway car which had been used in a wages snatch.
The businessman, who was a haulage contractor, said afterwards: “I’d do it again, for that kind of cowardly attack just gets my back up.”
This was despite him having to fork out for repairs to his van, which was damaged in the incident, which happened on Scout Hill, Dewsbury.
Steven said: “I had just driven past when, in my mirror, I saw the guard being swung around by a masked man who was wielding some kind of club. At the first junction, I turned my van around and headed back towards the scene.
“As I did so, the masked man got into a brown Sierra car and it took off towards me. I swerved to ram him but after the crash it got away by running onto the pavement.
“I turned round in a petrol filling station and chased after it but he lost me.”
The car was found abandoned nearby.
Steven added: “I am a businessman myself and would like to think if anything like that was happening to me, someone would step in to help.”
His actions were praised by police, who added that the security guard had already managed to foil the attempted robbery.