A drunk thug who knocked a shopper out cold with a "mighty blow" has had his sentence slashed by senior judges on appeal.

36-year-old Craig Birch, from Hazlemere, was jailed for 32 months at Aylesbury Crown Court in September last year after admitting assault causing actual bodily harm.

Birch launched a "vicious and cowardly surprise attack" on his victim in a shop in Oxford Street, High Wycombe, London's Appeal Court heard.

There was bad blood between the two men, said Judge Paul Batty QC, and Birch had managed to corner him in the shop.

"Birch walked up to him and delivered a mighty blow to the side of his head," he added.

"That caused his victim to fall to the floor and lose consciousness for two to three minutes".

Birch, of Lester Grove, had been drinking in the town at the time of the incident in July last year.

Judge Batty, sitting with Lady Justice Sharp and Mr Justice Haddon-Cave, commented on the savagery of the attack.

But, despite having a "truly breath-taking list of previous convictions", the top judges ruled that Birch’s sentence was “manifestly excessive" and reduced it to two years.