The Bexleyheath Academy assistant vice-principal who allegedly had an affair with a pupil has described the accusations as a "total unbelievable nightmare", adding he was "appalled" when they were first put to him.

Stuart Kerner, 44, from Aylesford, is accused of six counts of sexual activity with a child and two counts of sexual activity with a child by a person in a position of trust.

The relationship allegedly took place between March 2011 and November 2012.

The girl, who cannot be named for legal reasons, was 15 and 16 years old at the time.

The defence claims the girl made the whole thing up, creating the fantasy from details she picked up about Kerner's personal life from overheard conversations, assemblies, calendars and photos on his iPad.

Talking of the allegations, married father-of-one Kerner told Inner London Crown Court: "I was appalled, it was a total, unbelievable nightmare that someone was suggesting this.

"It didn't seem plausible that it was even happening."

It is alleged the religious education, ethics and politics teacher took the girl's virginity in an empty classroom at the school in February 2012, shortly after his wife had a miscarriage.

He said: "I think that was the occasion she had just had a miscarriage.

"It was shock and disbelief. That I would have been doing that at the time my wife lost the baby was ludicrous."

The girl claims that, on that occasion, Kerner got her out of her fourth period class in order to have sex with her.

She said the sex session went on well into the lunch period, lasting a total of one hour 45 minutes.

Kerner said: "That is not true and it is highly unlikely anyway.

"I am not a young man, I've never had sex for an hour and 45 minutes."

Responding to claims he kept his shirt, jacket and waistcoat on throughout, he added: "I think (if I'd been wearing all those clothes) I would have been completely wrecked. It is unlikely."

The court also heard the register in the school computer system had been changed to show the girl was present in her classes during that time, but Kerner also denied doing this.

The girl claims Kerner also had sex with her at his home in October 2012, picking her up from Crook Log Leisure Centre early in the day.

This is supported by evidence from Kerner's phone, the signal from which shows he was in the vicinity of the leisure centre at the time she claims.

However Kerner told the court he was going to Bexleyheath Academy to help out with an open day.

He added that although this was the case, he never ended up going into the school after receiving a text message from a colleague saying it was going "completely wrong" and to give it a "wide berth".

Kerner also addressed claims he used to stick his tongue at the girl, saying: "I stick my tongue out, I blew raspberries at the students all the time."

He denies all charges.

The trial continues.