Former world champion boxer Chris Eubank threatened to "deck" a lorry driver and swore before driving off in his vehicle, magistrates have heard.
The former boxing champion denies the charge against him
Scottish Courage employee Gary Chandler said Mr Eubank ran at him, swore and started a row before entering the cab.
Mr Eubank, 39, of Upper Drive, Hove, denies a charge of aggravated vehicle taking in a case being heard by Brighton Magistrates.
He has said the beer lorry blocked his way as he took his children to school.
The court heard several drivers were beeping their horns while the 35ft-long truck was being unloaded in February.
It was claimed that Mr Eubank was told the delivery was nearly finished, but he jumped into the cab, drove the lorry 150 yards along the road and hit a sign.
James Webb-Bowen, one of the men making the delivery in Sydney Street, said he tried to stop Mr Eubank when he was in the cab, but the former world super-middleweight champion pushed his arms out of the way.
Mr Webb-Bowen told the court: "The last time I tried to grab the key he said 'you do that again and I'll deck you'."
He said he stepped back and shouted to call the police.
Mr Chandler said the former champion swore and started a row
And then describing how Mr Eubank returned to his car, Mr Webb-Bowen added: "He jogged back up the road on the opposite side with his middle finger raised as he ran past.
"He raised his middle finger again as he drove past."
He said there was a child in the front seat of the car.
The court heard that a road sign was clipped by the Volvo lorry during the incident.
Prosecutor Madeleine Reardon said Mr Eubank had told his children that what he did was wrong.
She told the court he had admitted getting into the vehicle and driving and had claimed "it was the gentlemanly thing to do".
Ms Reardon also claimed Mr Eubank had said he did not remember causing damage but did offer to pay for it.
The case continues.