A Royal Air Force serviceman knocked an elderly man unconscious with one punch following an altercation, a court heard.

Standing trial at Ipswich Crown Court is James Sinclair, who is charged with causing grievous bodily harm to Thomas Cleary, 72, and assaulting his son Patrick Cleary, 31.

The court heard how the father and son had been drinking in Bury St Edmunds on November 23 last year after walking into town around 11pm.

Giving evidence during the first day of the trial, Patrick Cleary said the pair went out drinking together "quite often" in Bury.

He said the duo had visited the Kings Arms pub before venturing to The Grapes pub, and finished the night at The Gym bar in Risbygate Street.

Mr Cleary said he and his father had consumed six pints of lager each over the course of the night and they then went to get some chips.

They walked through the St Andrew's Street car park towards Tayfen Road and were met at the bottom of the steps of the car park by Sinclair, 24, who asked them for a lighter.

Thomas Cleary told Sinclair he didn't smoke before Sinclair swore at the men, the court heard.

Mr Cleary said he responded by swearing back before he crossed the road and was hit twice by Sinclair, who is based at RAF Honington.

"I tried to throw a couple of punches back but didn't land any on him," he said.

"He was moving like a boxer. I then put my hand up to stop a taxi and ran around the side of the car and asked the driver to call the police."

Mr Cleary told the jury he then saw Sinclair, of 27 Squadron, cross back over the road to where his father was still standing.

"He stood there looking at my father," Mr Cleary said. "Then punched him straight in the face. It was like he was punching one of those boxing balls you see at the funfair."

Mr Cleary added that his dad was "absolutely out of it" and he then went to ask the taxi driver to call an ambulance as well.

Thomas Clearly was initially taken to West Suffolk Hospital in Bury St Edmunds before being transferred to Addenbrooke's Hospital in Cambridge after a scan found serious bleeding on the brain and a fractured skull.

Sinclair claims he acted in self-defence during the incident.

The trial continues.