AN EX-POLICE officer has described the prison torment of a Welsh headteacher who claims he is innocent of abusing children in his care.The former detective, who was himself cleared of abuse, also said he was “100 per cent sure” of Derek Brushett’s innocence.Mike Lawson spent nearly three years in Albany prison on the Isle of Wight, where Brushett remains.But he was released earlier this year when the Court of Appeal quashed his conviction for sex abuse.The 62-year-old dad-of-three says although Brushett has been insulted by fellow inmates and has ‘dark days’, he continues to argue he is not guilty.Mr Lawson and another man, Basil Williams-Rigby, had been jailed for offences alleged to have been committed at an approved school in Merseyside but judges ruled their convictions were unsafe.Mr Lawson – who had spent 15 years as a police officer before going into teaching – was jailed after the Operation Care investigation into allegations of abuse in children’s homes in the 1970s and 1980s.His acquittal followed that of David Jones, now manager of Wolves football club, who was wrongly accused of child abuse after being arrested by officers working on the same inquiry into the same school.