The jury took four hours to find Benjamin Laing, 25, from East Ham, east London guilty of shooting Mr Manwaring, 62, and strangling Ms Manwaring, 24, on 23 April last year.
The unanimous verdicts were greeted with applause and cheers from the public gallery. Mark Manwaring, Mr Manwaring's son, wept and hugged Gordon Healis, Ms Manwaring's fiance. Laing's family, who were given police protection in the gallery, also wept.
After the jury returned their verdicts, Judge Robert Lymbery QC told Laing he destroyed a family to satisfy his 'desire for enrichment'. He added: 'You are a dangerous man capable of extreme violence. You are utterly ruthless. I have no alternative but to recommend you serve a minimum of 25 years.'
Judge Lymbery said Laing had behaved arrogantly during the trial and had shown no remorse. 'You even managed to turn on the tears when you described seeing a foot on the wasteland during your false story. Fortunately the jury weren't fooled.'
As Laing was led to the cells by four prison officers, a man in the public gallery shouted: 'I hope your rot in hell, you bastard.' Laing turned round and gave a two finger sign.
The court heard that Laing duped his way into Matthew Manwaring's house by posing as a prospective buyer for his son's car. He shot Mr Manwaring in the chest at point blank range and then tortured and raped his daughter Alison before strangling her with his hands.
After dismembering their bodies in the bathroom, Laing buried them in his girlfriend's garden. Judge Lymbrey ruled that the photographs of the dismembered bodies were 'too disturbing' to be shown to the jury.
Before sentence was passed, Michael Stuart-Moore QC, for the prosecution, told the judge Laing had two previous convictions for armed robbery and deception. Anthony Scrivener QC, for the defence, said Laing would appeal against the verdict.
Although Laing has always protested his innocence, he changed his story three times. After his arrest Laing admitted buying the car, but he told the police he left the Manwarings in 'good health'. When the police discovered the bodies, Laing blamed the Fijian Freedom Fighters, a terrorist organisation, but the court heard they do not exist.
During his four days in the witness box, Laing said he had been framed by Mark Leslie, his best friend, Neil Philips, another friend and Frank Cohen, a car thief. Mr Stuart-Moore told the jury Mr Cohen was 'a figment of Laing's vivid imagination'.
Mark Manwaring, 27, an RAF navigator and Gordon Healis, 31, a hospital porter, have both received counselling from the RAF and attended the trial everyday. After the verdict, Mark Manwaring said he could not describe his feelings for Laing and called for a referendum on the death penalty. 'If Laing comes out people will be waiting for him and justice will be done properly.'