Former Bexleyheath Academy assistant vice-principal Stuart Kerner was “groomed” by the girl he today avoided prison for having a sexual relationship with, a judge has said.

The 44-year-old fought back tears as he was handed an 18-month sentence, suspended for 18 months, over the affair, which first became sexual when the victim was 16.

Dressed in a grey suit, blue shirt and blue tie, Kerner embraced his wife Katy as he left the dock at Inner London Crown Court after Judge Joanna Greenberg QC passed sentence.

He was driven away in a car outside court and neither he or his wife, who broke down when she heard her husband was to walk free, made any comment to the press.

Kerner was given eight months for his first conviction for sexual activity with a child by a person in a position of trust and 10 for the second.

The father-of-one, from Aylesford, was found guilty of both on December 5 after a trial lasting more than two weeks.

He was found not guilty on four counts of the same charge, and of two further counts of sexual activity with a child.

Judge Greenberg chose not to jail Kerner as the victim, who was present at court but cannot be named for legal reasons, had been the one who had "groomed" the teacher and "stalked" him, she said.

Judge Greenberg told a packed court room: “It is a tragedy that somebody like you committed offences of this nature and has come to be sentenced.

“The victim pursued you and formed an attachment to you that was not something that you sought.

“Her friends describe her as stalking you.

“There is no doubt that she became obsessed with you and given the jury’s verdict, and the evidence of the witnesses, that was an obsession she had harboured before February 2012 when you committed the first offence.

“What makes this case so different from the many cases of this type is that I find no evidence that you groomed or encouraged the victim into a relationship and if grooming is the right word to use, it was she who groomed you and you gave way to temptation at a time when you were emotionally vulnerable because your wife had suffered a miscarriage.”

Prosecutor Warwick Tatford told the court Kerner took the teenager’s virginity on a yoga mat in an empty room at Bexleyheath Academy on February 28, 2012, the same week his wife miscarried their second child.

School records had been tampered with to show the then 16-year-old was in lessons when in fact she was having sex with Kerner, 41 and 25 years her senior at the time, in an empty classroom with the door blocked by a table.

This first offence for which Kerner was convicted was followed by a second, when the pair slept together three times at his home on October 3, 2012.

The victim’s version of events was backed up by mobile phone records matching where she claimed the pair were at certain times of the day and by the fact she could accurately describe the layout of Kerner’s home.

But Judge Greenberg made clear the jury of six men and six women found Kerner not guilty of the six charges for which there was no such corroborating evidence because they did not trust the victim as a witness.

She said: “The victim showed no compunction about telling significant lies when it suited her to do so and, when caught out, appeared to show some pride about having lied.”

One such deception involved the victim wearing a bandage on her chest for several weeks in order to pretend she had been hit by a car, which had never in fact happened.

Judge Greenberg said: “It is apparent that she had an insecure family life but against that she was obviously an intelligent, manipulative girl who was capable of manipulating those she chose to manipulate.”

Speaking directly to Kerner, judge Greenberg said: “You have an exemplary character and a history of public service.

“Your professional career, which you nurtured for more than 20 years, is ruined and your reputation lost.

"However much sympathy I have with you and the way you gave in to temptation, the offences are so serious that they cross the custody threshold."