Daniel Dighton, 35, was told he would have to serve a minimum of 15 years and would only be released if it was thought he was no longer a danger. Dighton was cleared of murdering former headmaster Barry, 61, and Elizabeth, 60, but the Old Bailey jury found him guilty of manslaughter on 11-1 majorities, on the grounds of diminished responsibility. The court was told he attacked his parents with two knives at the family home in south Croydon, south London, in September last year. He flew into a rage after his parents returned from a shopping trip to find him still in bed and hungover. He stabbed his mother 28 times and then stabbed his father four times when he tried to help her. Dighton was sentenced to two indefinite terms to run concurrently for his "savage" crimes. A doctor told the court Dighton may have been suffering from an acute stress reaction when he killed his parents. Judge Timothy Pontius told him: "This was a truly horrific act of savagery." He said Dighton was not some badly-treated child who snapped. "Yours was always a loving and close-knit family. Your parents were affectionate, generous and loving." Dighton was regarded as being spoilt by his parents but had fallen short of their expectations. He had chosen to live an "indolent life", content to live at home and be supported by his parents. "It is hardly surprising your parents felt at the end of their tether," said the judge. Joel Bennathan, QC, defending, said Dighton had never been in trouble before and had never shown any signs of violence. He had shown genuine remorse at killing the parents he had depended on. The Dightons had both worked at the independent Elmhurst boys' prep school before retiring in 2006. Dighton had struggled academically and had not been able to live up to their expectations. He had been spent his days in bed and his evenings drinking whisky in a local pub. Prosecutor Crispin Aylett, QC, said: "A quarrel broke out. A routine argument quickly got out of hand."