A retired headmaster who had been found guilty of gross indecency with a 14-year-old boy has had his conviction nulled due to police and Crown Prosecution Service errors.

John Coatman, 76, a former headteacher at St Andrew's Church of England High School in Waddon appealed to the High Court to overturn his conviction for historic sexual abuse at the Old Bailey in August.

Senior judges this month overturned the jury’s verdicts that Mr Coatman, who had also been honoured by the Queen for his services to young people, had sexual activity with the teenager in the 1970s.

Three judges at the Royal Courts of Justice quashed his outstanding convictions on April 6, ruling that Mr Coatman should not have faced the charges under section 1 of the Indecency With Children Act 1960 and section 13 of the Sexual Offences Act 1956.

The Right Honourable Lady Justice Hallett DBE stated: “Both (the police and Crown Prosecution Service) were wrong (to pursue these charges).

“The appellant could not be charged with offences under section 1 because of the age of the complainant at the time and could not be charged with offences under section 13 because they were time barred.”

Mr Coatman could not have committed an offence against a 14-year-old boy in 1973 under Section 1 of the 1960 Act because the law did not relate to alleged victims of that age until 2001, Lady Justice Hallett ruled.

Buggery charges levied against Mr Coatman under Section 13 of the 1956 Act – provided at the time under the heading ‘Indecency with Men’ – were ‘inapt’, the judge ruled, because the alleged conduct amounted to an assault towards a victim, rather than a sexual act with another man.

Lady Justice Hallett added: “Over the last few years this court has issued repeated warnings about the dangers of poor drafting of indictments in cases of alleged 'historic sexual abuse'."

A Crown Prosecution Service (CPS) spokesperson said: “We have contacted the complainant in this case to explain the issue and apologised.

“The CPS has issued advice to our specialist sexual offences prosecutors about the appropriate offences to charge in these particular circumstances, to reflect the changes in the law and recent Court of Appeal judgements.

“Cases currently before the courts have also been re-checked to ensure the error does not happen again.”