A man grabbed a shop worker, punched and headbutted him repeatedly after being told he could not exchange a fishing net.
David Furlong flew into a rage and assaulted the worker at a shop in Mill View, March, a court heard.
Furlong, 33, had demanded money from the till after being told the net he had broken himself could not be exchanged for a more expensive net from the shop.
He grabbed the man, punched him repeatedly to the head and face and headbutted him, causing bruising and swelling.
The worker gave Furlong £65 from the till, and he left.
On Friday, at Cambridge Crown Court, Furlong, of Main Road, Parson Drove, was jailed for three years having pleaded guilty to the robbery on 30 July last year.
He was also given a five-year restraining order.
PC Stephen Elliot said: “Furlong behaved like a thug, unleashing a vicious assault on the shop worker who was just doing his job.
“The violence was completely disproportional and unprovoked, and the sentence handed down reflects the severity of the attack.”
