Jealous Joseph Longstaff lashed out when he saw his 16-year-old "lass" dancing with his friend Graeme Pounder while they were out celebrating a birthday at The Loft nightclub in Durham in March.

Newcastle Crown Court heard how Longstaff, who had downed 18 pints, stormed on to the dance floor and threw a single blow which immediately knocked Graeme out.

Graeme, 21, who lived in Stanley, suffered a massive subaracnoid haemorrhage and died in hospital the next day.

The court heard on the night Graeme was killed, he and his friends, including Longstaff, had been out since noon celebrating another pal's birthday.

Longstaff had rowed with his girlfriend before they got into the club when he saw her dancing with Graeme in one of the bars.

The court heard he sent a series of text messages to her while she was dancing.

Longstaff, of Hollyhill Gardens, Stanley, was originally charged with murder but admitted the lesser charge of manslaughter.

The court heard Graeme's body showed no signs of the assault at a post-mortem examination, indicating the punch could have been little more than a glancing blow.

Judge David Hodson said he accepted Longstaff had not intended to kill or cause serious harm to his friend.

But the judge said: "There can be no doubt your friend would still be alive but for the punch you threw."

Defence barrister Paul Sloan QC said Longstaff is "racked with guilt" over the death of his friend and is still struggling to come to terms with what he did.