A student accused of the manslaughter of a gay man says he hit the victim because he thought he was attacking a girl.

Joel Alexander, 19, a student at East London University, told the Old Bailey today he hit 62-year-old Ian Baynham when he saw him in a confrontation with 18-year-old Ruby Thomas, from Lichfield.

Mr Alexander, Ms Thomas and 18-year-old Rachel Burke, of Three Oaks, East Sussex, are all accused of Mr Baynham’s manslaughter.

He was attacked in Trafalgar Square while on a night out with a friend in September and died of head injuries 18 days later.

According to Press Association, the jury heard today that Mr Alexander was in the area celebrating his girlfriend’s birthday with friends.

He said Ms Thomas had been “lairy [and] mouthy” earlier in the evening and he had prevented a confrontation with another group of youths.

Later, he said, he heard Ms Thomas shout “something like ‘batty boys'” at Mr Baynham and his friend Philip Brown.

Mr Alexander told the court he saw Mr Baynham turn around and say something along the lines of “I may be gay but…”.

He said the pair then walked towards each other and heard raised voices, before the contents of Ms Thomas’ handbag fell to the floor.

He said he then saw Mr Baynham’s throw his hand towards Ms Thomas.

Mr Alexander said: “What I was perceiving was a grown man hitting a girl. She was more subdued; she wasn’t as lairy any more. It looked to me as if the man was starting to get the better of her.

“That’s when I thought I had to act. I lunged at Mr Baynham and hit him with my right hand.”

He said he struck Mr Baynham with a “moderate” blow and did not believe he would be knocked to the ground.

Earlier in the trial, witnesses said they saw Ms Thomas and Ms Burke kicking Mr Baynham as he lay on the floor.

Yesterday, the Old Bailey heard that Ms Thomas was involved in an attack on a bus driver near the same spot in December 2007.

The three defendants are pleading not guilty to manslaughter.

The trial continues.