A headteacher who had a conviction for physically assaulting pupils quashed by the Court of Appeal, has spoken out about how his life was “turned upside down”.

In April last year Derek Cooper, 78, was found guilty of assaulting two boys at Underley Hall school in Kirkby Lonsdale, Cumbria, in the 1970s and 1980s.

Advice: How to deal with false allegations

Watch: ‘Utter devastation’ of falsely accused teachers

Story: ‘I ended up taking an overdose’

After more than nine months in prison, he was released last month, after judges ruled that his conviction “cannot be regarded as safe”.

Mr Cooper faced seven charges of assault and two of child cruelty, but much of the case against him was rejected by the jury and he was found guilty of only two offences.

The appeal court later overturned his conviction because it said jurors may have misunderstood what Mr Cooper would have had to have done to be guilty.

“My life has been turned upside down,” Mr Cooper told The Sunday Times. “The Court of Appeal has confirmed that I was wrongly convicted. This was a miscarriage of justice.”

Mr Cooper was accused of headbutting one pupil, and assaulting a second pupil in the school dining room, but maintained that the allegations were “fantasy”.

“I was absolutely stunned when the jury found me guilty,” he said. “I could not even remember one of the people making allegations.”

“Many of the people I would have liked to call as witnesses were dead and records had been destroyed,” he said. “After a lifetime of dedicated service to needy children, I had become a criminal. I discovered it is almost impossible to prove your innocence about events so long ago.”

Describing his time in prison, he said: “I am a 78-year-old man. I have never endured anything like this before. The [cell] door clangs shut and you’re on your own. I couldn’t understand why I was there.”

He added: “The stress was awful and still is. I had an unshakeable belief in the British justice system, but I was in prison for almost 10 months. The memories of that have changed my life for ever.”