AN ASSISTANT headteacher accused of having a sexual relationship with a schoolboy told jurors the teenager made it all up in a blackmail plot.

Adam Williams gave evidence on day three of his trial at Oxford Crown Court yesterday.

The married father-of-two admitted sending more than 7,900 messages to the boy between May and December last year, but denied any sexual encounters took place.

Williams, who was director of sixth form at an Oxfordshire school, said it was “an extremely stressful place to work” and admitted using Grindr, a mobile phone application to connect gay men with one another, as a form of “escapism”.

The 35-year-old, who is also a national list football referee, told jurors he began communicating on Grindr in late spring 2011 with someone who told him he was 20 and from Oxford.

He admitted finding out on June 15 that the “man” was in fact a teenage school pupil but carried on texting him. Williams said he did so because the boy was threatening to distribute naked pictures the teacher had sent him if he ended the contact.

He said: “Words cannot really explain my reaction (to the threats), he basically had control over me.

“I was petrified, frightened, scared.

“Yes, I made a mistake going on Grindr but from that point onwards I wasn’t myself.”

Jurors were shown a series of texts between the pair in which Williams appeared to be flirting and contributing to sexual conversations, but he said he did so because simultaneously on Grindr he was being threatened by the boy with exposure if he stopped the communication.

He said the texts of a sexual nature, which showed a mutual desire to meet for a sexual encounter, were part of “a fantasy conversation”.

Pressed as to why there would be two streams of communication with the same person, Williams said he believed the boy knew that unlike texts, Grindr messages could not be traced and re-read at a later date.

Asked about each of the seven alleged sexual liaisons with the boy in October and November last year, Williams, of Ruardean Walk, Cheltenham, denied any of them took place. The boy, said Williams, whose wife was pregnant at the time, took him to Tesco in Cowley on November 24 last year.

Williams’ car was captured on camera at the store that night and the boy’s debit card was used there at about the same time.

But the defendant denied being with the teenager at the time.

He said he was “just driving around” to “try to forget about” a stressful day before meeting his mother at Oxford train station.

Asked why he made no comment in two police interviews Williams said: “I haven’t ever been in that situation before.

“I was taking advice from the solicitor.”

The trial continues.