In the early hours of July 24, 2016, Brayden Craig Hayes, 23, of Cygnet, was with his girlfriend at the Observatory Bar, a nightclub on Hobart’s waterfront.

Mr Hayes’ counsel told the court that the complainant and a group of his companions pushed past Mr Hayes and his girlfriend at the top of the stairs leading up to the bar.

It was said that this caused Mr Hayes’ girlfriend to fall down the stairs.

The accused then walked 150 metres up Murray Street towards Despard Street, another Hobart nightlife hub.

The defence counsel said Mr Hayes then saw the man who had pushed past his girlfriend, which is when his “emotional state intensified”.

Mr Hayes confronted the complainant and headbutted him, causing what the prosecution described as a “serious” tooth injury.

It was then that Mr Hayes moved further down the road, where another altercation was developing.

He was not a participant in the second fight but he was there arrested by police.

According to Crown Prosecutor Tony Jacobs, the complainant required an expensive root canal procedure following the assault.

Mr Hayes’ counsel said the assault was “out of character” and that his client was “extremely remorseful”.

Mr Hayes, a qualified electrician, rose to prominence when he embarked on a charity run in March this year after losing a bet.

In January, he wagered that if the Hobart Hurricanes beat the Melbourne Renegades in the Big Bash cricket league, he would run from Hobart to Burnie in his underwear.

The team ended up staging a remarkable come from behind win.

The Run for a Cause raised more than $20,000 for Motor Neurone Disease Tasmania and Diddy’s Day Out, a charity supporting a young Tasmanian girl with a rare form of bone cancer.

Mr Hayes will appear for sentencing on Thursday.