A sadistic fantasist has been sentenced to life in prison with a minimum term of 39 years for murdering a vulnerable gay man in his home while posing as an MI5 agent.

Jason Marshall, 29, stripped Peter Fasoli, 58, and gagged and smothered him with cling film, before stealing cash and cards from the victim and setting light to his flat to cover his tracks in January 2013.

Sentencing Marshall, who was found guilty of murder and arson, at the Old Bailey on Tuesday, the judge, Nicholas Hilliard QC, said: “I am sure you were motivated by a desire to cause Mr Fasoli pain without his consent … You tortured him for so long because you enjoyed it so much.

“The dominant elements of your motivation for killing Mr Fasoli were robbery and sadism. I’m sure that you can have felt no remorse whatsoever for what you have done. On the contrary, you derived pleasure from it.”

Marshall, dressed in a light pink shirt, was emotionless as the sentence was handed down.

He met Fasoli, a computer repairman who lived alone and had a heart condition, on Badoo, a dating website. Marshall, who has Asperger syndrome and epilepsy, arranged to meet him at Fasoli’s flat in Northolt, west London, on the pretext of a bondage sex session, but with a plan of robbing him.

He stole £780 in the days after Fasoli’s death and used the victim’s bank card to buy a flight to Italy, where he killed a second man and attempted to murder another in Rome.

For nearly two years, Fasoli’s death was believed to be an accident, until his nephew found hours of harrowing footage of his murder stored on Fasoli’s hard drive. This was shown to jurors.

Marshall, from East Ham in east London, who was serving 16 years for the attacks in Italy, claimed to be suffering from amnesia.

Tomas Quinn, defending, said his client had a “bizarre” history of impersonating police officers and ticket inspectors.

Ed Brown QC, prosecuting, told the Old Bailey that Fasoli’s sister Ann Murgatroyd had come to the court, but her son Christopher, who discovered the footage, was still too upset.

“Mrs Murgatroyd is here. The finding of the very distressing footage for her son, the nephew of the deceased, has plainly had a significant impact on both parties,” he said.

“Her son has not felt able to come and he continues to be distressed by what he saw and therefore his part in this sorry affair.”

Sally-Anne Russell from the Crown Prosecution Service said: “Jason Marshall murdered Peter Fasoli after being invited into his home. He suffocated him before lighting a fire to cover his tracks.

“If it hadn’t been for Mr Fasoli’s laptop footage, Marshall may have escaped justice. That video, which was extremely disturbing, clearly showed Marshall’s true intentions and undermined any false account he could give.”