Nerijus Vaitkevicius headbutted the 17-year-old because he thought he was being filmed.
City magistrates were told yesterday (Monday) that the complainant had been at a Bretton skate park when Vaitkevicius arrived with others at about 5.45pm on August 30, 2019.
Prosecutor Paul Brown said: “[The victim] was sitting down and on his phone talking to his friend. At that point he sees a large group of males arrive from the direction of Bretton Water Park.
“They are known as the ‘Central Boys’ because they hang about at Central Park.
“He told his friend on the phone that he thought they were there to see him because he’d had issues with them the previous day.”
Vaitkevicius, who was also 17 at the time, kicked the complainant’s scooter and then headbutted him.
“He said he did it not because of any previous incident but because he thought the complainant was filming him and his friends,” said Mr Brown.
The court was told that the victim was kicked and punched several times, possibly by others present, but Vaitkevicius only admitted to the single headbutt.
In a statement read to the court, the victim said: “I would never in a million years walk up to someone and start attacking them for no reason.”
He said the assault had left a lifetime scar on his head which he is constantly asked about, which makes him feel uncomfortable.
Vaitkevicius, of Cavendish Street, had denied a more serious initial charge but last month pleaded guilty to assault occasioning actual bodily harm.
Jeremy Roberts, mitigating, said the matter could have been dealt with much earlier and had his client been dealt with in a youth court nearer the time of the offence he would have received a referral order.
“He’s had this hanging over him for two years, during which he’s stayed out of trouble,” he said.
The solicitor said of the incident: “He did not have any particular axe to grind when he got there.
“He’s very sorry that he did lose his temper and he says that was because he felt he and others were being filmed.”
Mr Roberts said it was unfortunate that no-one else had been charged in connection with the incident, despite names being supplied.
“The majority of the injuries would have been caused by others,” he said.
The bench described the attack as “brutal and unprovoked” but took into account Vaitkevicius had no previous convictions and had not been in trouble in the meantime.
The defendant was given six months’ custody, suspended for 18 months.
He must do 120 hours’ unpaid work and 40 rehabilitation activity days.