Ross Kerr knocked his victim, Peter West, out cold with a single punch at the British Showjumping Association’s Scottish Branch annual awards ball in Airth Castle.
Shocked fellow revellers put Mr West (49) into the recovery position and called an ambulance while Kerr (23) and his then girlfriend, Holly Cunningham, were “ushered out”.
Kerr was arrested 40 minutes later in the bedroom he was sharing with Holly (26) at the hotel and spa near Falkirk.
Stirling Sheriff Court heard that Mr West was taken to the nearby Forth Valley Royal Hospital and then transferred to Monklands General Hospital where specialists found a fracture and bruising to the left hand side of his jaw, and ordered him not to chew for six weeks while it healed naturally.
Prosecutor Sarah Lumsden said the incident occurred at around 1am on January 15, 2016.
She said Mr West, his wife Sarah, a 14-year-old girl and 10-year-old boy were attending the ball, as were Kerr and Miss Cunningham.
Miss Lumsden said the 14-year-old was on crutches, with a cast on her right ankle. The depute fiscal said the Wests were seated at a table with the 14-year-old and a friend.
She said: “Peter West had noticed the girlfriend of the accused walking around the venue in a very drunken state. She walked over to the West’s table followed by her boyfriend, Kerr.
“She spilled a drink over Peter West and knocked over a few glasses on the table – that was accidental, probably due to the fact that she was intoxicated.”
Miss Lumsden said the teenage girl asked Miss Cunningham “what was happening”. She said: “At this, Miss Cunningham began to shout abuse at the girl who pointed out to Miss Cunningham that she was 14 and on crutches.
“Words were heated between the pair, such that Peter West stood up and said to Miss Cunningham that she’d had too much to drink and advised her to go to her room.
“At this, Mr Kerr approached Mr West and punched him to the left hand side of his jaw, causing him to fall to the ground. He was rendered unconscious for a short period of time.”
Miss Lumsden said the assault was witnessed by the 10-year-old boy, among others.
She added: “Another witness placed Mr West in the recovery position and contacted an ambulance and Miss Cunningham and the accused were ushered out of the venue. Both returned to their room and the police were contacted.”
Kerr initially denied throwing a punch and told officers: “I was just trying to get the guy, who was pulling at my top, off.”
In court, Kerr, of Balgreggie Park, Cardenden, Fife, pleaded guilty to assault to severe injury.
Murray Aitken, defending, said it was “unclear” whether the injury was caused by Kerr’s punch, or Mr West’s resulting fall.
He said: “Witnesses describe him as falling awkwardly and landing heavily. It may not matter much and Mr Kerr of course accepts that he caused the injury.
“It’s just a question of the forcefulness or otherwise of the blow that was impacted.”
Sheriff Wyllie Robertson told Kerr that background reports were “inevitable” and deferred sentence until November 30.
Kerr’s bail was continued.
Last year (2015) Kerr was fined £600 and banned from driving for 16 months after admitting driving with excess alcohol in Dundee.
Dundee Sheriff Court heard that Kerr was “a successful bodybuilder” who normally did not drink much, but had been out with a friend celebrating success in a bodybuilding competition and “misjudged” the amount of alcohol he had taken.
Kerr’s official Facebook page describes him as “world-renowned Junior Professional Bodybuilder Ross Kerr”.