DC Laura Rainbird, who investigated, said: “This was a nasty attack on a complete stranger which left him with serious injuries.

Jonathan Chidzoy, 20, of London Road, St Ives, was in McDonald’s in Fitzroy Street on November 10, 2018.

Whilst there, he had an argument with another man and his group of friends, before he walked out with three of his own friends.

As Chidzoy left McDonald’s, the man he had argued with, stuck his middle finger up at him and his friends and followed them to the door.

The man stood at the doorway to the fast food restaurant between two members of door staff and watched Chidzoy and his three friends walk away.

However, Chidzoy then came back, walked up to the man and punched him to the side of the face. The man had his hands by his side as this happened.

The man fell to the ground and Chidzoy immediately ran from the scene as the two door staff tried to restrain him.

The victim remained in McDonald’s for around 20 minutes before he left and came across an officer on patrol in the city centre.

He explained what had happened and police chased and caught up with Chidzoy, who was arrested on suspicion of assault occasioning grievous bodily harm (GBH) without intent.

The attack left the man with a broken jaw which required surgery.

In police interview, Chidzoy claimed he hit the man in self-defence after feeling threatened by him as he didn’t know “what he was capable of”.

Chidzoy was later charged with the offence and pleaded guilty at Cambridge Crown Court on September 1.

On October 6, at the same court he was handed a two-year community order and a 50-day rehabilitation activity requirement. He was also ordered to pay £3,000 in compensation to his victim.

DC Laura Rainbird, who investigated, said: “This was a nasty attack on a complete stranger which left him with serious injuries.

“Chidzoy’s behaviour was unacceptable and no-one deserves to be assaulted in this way.”