A police officer who worked with the West Midlands family protection unit investigating child abuse cases was jailed for five years today after being convicted of a serious sex offence and indecent assault on a 14-year-old boy.

The offences were committed more than 20 years ago and only came to light when detective constable Peter Cooper, 58, of Edenfied Close, Redditch, came face-to-face with a former Army cadet he abused.

The principal witness who gave evidence said cadets had been "brainwashed into thinking that the abuse was normal."

Now in his 30s he said in evidence that he went to the police with his allegations because he had reached a point in his life where he could no longer keep it quiet.

Two other former cadets also gave evidence at the trial and spoke of a "culture of abuse" which involved a number of instructors who held officer rank.

Cooper - who was also a former Army captain - was stationed at Bournville Lane police station, Birmingham.

He was convicted in July and cleared of five other allegations of sexual abuse.

Judge Simon Tonking, at Stafford Crown Court, told him: "Both of these offences were committed in your home, ostensibly to give him military equipment.

"That demonstrates your premeditation and the level of trust he put in you and that nothing was going to happen,

He said he was "not only Army captain but also a policeman."

"The fact that you were a policeman appeared as a glamorous role and made him look up to you. As a result, significant harm was caused.

"The victim has undergone counselling and many years followed before he exposed what happened. You are an unimpeachable husband and father and I bear in mind the effect a prison sentence will have on your family.

"The sentence of imprisonment will all the more severe for a man in your position. You will be banned from working with children for the rest of your life.

"The least sentence I can pass is one of five years."

The media could not report the trial after the judge imposed an order under the Contempt of Court Act because another man was due to go on trial for similar offences. The charges were dropped.

Cooper joined the force in 1973 after serving with the Royal Corps of Signals. He was a firearms officer and spent some time in the Regional Crime Squad before joining the family protection unit. He was regarded by colleagues as "one of the best in the unit" at interviewing suspects.

He joined the Army Cadet Corps and rose to the rank of captain but left in 1987 to spend more time with his family.

Christopher Millington QC, defending, said: "This was a serious breach of trust and the defendant has to face a substantial period of imprisonment. He is a man of exemplary conduct. He has a son of 18 and a daughter of 17.

"His home which has a #150,000 mortgage will have to be sold and the family's financial position will be precarious.

"The sentence on him will have a particular type of effect and a sentence of a police officer will be hard.  He will probably not only have to serve it as a sex offender but as a police officer in virtual isolation."

Miss Rachel Brand QC, prosecuting, told jurors Cooper was "plausible and intelligent but lied when he denied sex allegations.

"Throughout the intervening years, he must have thought he had got away with it but the truth is out at last. The damage he did was far-reaching which caused an emotional turmoil and lasted for many years."