A motorist blocked the path of a mugger who had just snatched a handbag from a woman in Cleckheaton.
The victim, a 60-year-old woman, had been walking on the Spen Valley Greenway when a man grabbed her from behind.
After a brief struggle he ran off with then bag onto Whitechapel Road, but dropped it after two members of the public tried to intervene, one by clocking off his escape with the car he was driving.
The suspect then fled onto Turnsteads Drive.
The incident happened on Tuesday February 11 between 1.30pm-1.40pm and Huddersfield CID are appealing for witnesses or anyone with information to come forward.
The man they are looking for is white, in his mid to late 20s, 5ft 11ins tall, of medium build and with a lopsided mouth.
He was wearing a grey woollen hat with a peak, grey jacket and grey bottoms.
DC Andy Clayton of Huddersfield CID, said; “We are appealing for witnesses to this offence, including the driver who tried to pull his car in front of the suspect to cut off his escape.
“Anyone who saw the incident or can identify the attacker should contact myself at Huddersfield CID on 101 or CrimeStoppers anonymously on 0800 555 111.”