A muscular thief landed his victim in hospital after attacking him in Dunstable last week.
The shocking assault took place in Brewers Hill on Thursday, February 11.
At around 7.50pm the victim entered a garage block to put his motorbike away.
As he turned to close the door, a man approached and ordered the victim to hand over his wallet before attacking him.
As a result, the victim was left with injuries that required hospital treatment.
The offender is described as white, about 30 years old and around six feet tall with a muscular build.
He was wearing a grey tracksuit top with the hood up, grey tracksuit bottoms and had a white scarf covering the lower half of his face.
Det Con Jenny Buckley said: “Any robbery is unacceptable, and this is a particularly nasty incident which has understandably left the victim shaken.
“I am keen to hear from anyone who was in the area at the time of the offence who may have seen a man matching the description, or from anyone who has any information about who is responsible.”
Anyone with information is asked to contact DC Buckley on 101 quoting crime reference number JD/5976/16. Alternatively, call Crimestoppers anonymously on 0800 555 111.