A former boarding school owner whose conviction for alleged pupil assaults was quashed by top judges has branded the £2.3 million police operation which brought him and other ex-teachers to court ’a scandalous waste of money’.

Cumbria Constabulary announced last month that an investigation into alleged historical abuse at south Cumbria residential schools would conclude on February 28.

Operation Tweed began in 2014 and resulted in Derrick Cooper, who now lives in Hillberry Green, Douglas, the former owner of Kirkby Lonsdale’s Underley Hall in south Cumbria - and four staff members - standing trial at Carlisle Crown Court early last year.

A sixth man was deemed too ill to face trial.

The four employees were acquitted.

Mr Cooper was initially convicted of assaulting one boy and cruelty to another, receiving a 20-month jail term.

But after serving more than nine months in custody, Mr Cooper was cleared after judges at the Court of Appeal in London concluded his conviction could not be regarded as safe.

Speaking publicly for the first time since his release from prison, Mr Cooper said of his initial conviction: ’After a lifetime of dedicated service to needy children, I had become a criminal.’

He recalled: ’Over a protracted period I was interviewed, charged and had to undergo an eight-week trial. We had not done what was being said.

’The stories that the complainants gave in their witness statements were entirely different to what they said when they came to court. There was no evidence against me or any of the others aside from what the complainants themselves said.’

The jury’s initial guilty verdicts, Mr Cooper says, left him absolutely stunned. The whole experience, he said, was devastating.

’I am a 78-year old man. I have reached a stage of life where my main concerns are meeting the next doctor or hospital appointment. I have never endured anything like this before; the stress was awful and it still is, my life had been turned upside down.’

Of custody, he recalled: ’The (cell) door clangs shut and you’re on your own. I couldn’t understand why I was there.

’That was my main thought. How can I be in prison when there was no evidence against me?

’I was miles away from my family and not allowed any visitors to start with. My wife looks after her 100-year-old mother, so I knew she would never be able to visit. I can’t tell you how alone I felt.’

He added: ’I had an unshakeable belief in the British justice system. But the belief is put to the test when there is a miscarriage of justice, albeit one (since) corrected.

’I did absolutely nothing wrong. I was - as the Court of Appeal resoundingly confirmed - wrongly convicted. I should never have been in prison in the first place. This was a miscarriage of justice. Nevertheless I am hugely relieved.’

Cumbria police said its officers worked ’diligently and professionally’ during Operation Tweed which, it said, was ’carried out thoroughly and impartially’.

As part of its investigation, six former teachers at Witherslack Hall, Grange-over-Sands, were also charged.

Two men were convicted of single child cruelty charges by a jury, and sentenced; three were acquitted by jurors. One was cleared before trial.

Mr Cooper added: ’There are massive lessons to be learned about the investigation, the CPS decision to prosecute me and the court process. We all felt that fairness had gone out of the window. Driven by an unquestioning belief in what the accusers told them the whole system seemed hell bent on our convictions.

’Without any evidence at all how can people be put through a trial and in my case convicted and imprisoned? I know it sounds incredible but that is exactly what happened.’

Describing Operation Tweed as a witch hunt, Mr Cooper said: ’This has been a scandal and a scandalous waste of money. There needs to be a proper review of what has gone on from start to finish.’