A "layabout" son was jailed indefinitely for public protection today for the manslaughter of his retired teacher parents.
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 Campden Road, 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 spending 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.
"The defendant armed himself with two knives, stabbing both of his parents to death in an attack of terrible ferocity."
After neighbours heard screams, police followed a trail of blood and found Dighton hiding in the loft wearing a Crystal Palace football shirt. His hands were still covered in blood.
The living room was covered in blood with Mr Dighton in an armchair and his wife on the floor.
Pc Michael Matthews said Dighton told him: "It's just an argument that got out of hand. I don't normally lose my rag like that."
A few minutes later, he had added: "I just wish I could turn back time."
Dighton later told a psychologist that he lost control when his mother had allegedly called him an idiot.
As he attacked her, Mrs Dighton had shouted at him to stop. He said: "I shouted something back and she said 'What are you doing Danny? I love you'."
Dighton had replied: "I know, I love you too."
The Dightons were described as "perfect companions". They were season ticket holders at Kent County Cricket Club and Crystal Palace Football Club.
After their deaths, staff and pupils paid tribute to them on a website.
His elderly grandmother Olive said his parents spoilt Dighton. They had "waited on him hand and foot".
The regulars at the Folly pub thought he was a popular, intelligent man as well as being good company.
No one realised he was still living at home and was dependent on his parents.
The Dightons helped their only child get a qualification for teaching English as a foreign language, and soon Dighton was telling his pals that he had a teaching job in Thailand.
But it was not true and Dighton had to go through an elaborate charade, lying low at home and at the Dightons' second home in France.
When he did "return" after a month, he plastered on fake tan - causing his mother to complain about her dirty sheets.
He explained that his mother had died and he was attending her funeral.
But when his friends went to pay their respects, they could find no funeral and no wake.Reuse content