A computer repairman was filmed begging for his life after he was allegedly attacked by a roleplay policeman - who then set his Northolt home on fire to cover his tracks.
Fantasist Jason Marshall, 28, is accused of the horrific murder which was inadvertently filmed by the victim, while Wagner and Mendelssohn played on Classic FM in the background.
Jurors at the Old Bailey watched footage of 58-year-old loner Peter Fasoli begging for his life when he was tied up, gagged and smothered with cling film after Marshall tricked his way into his home in January 2013, the court heard.
Afterwards, Marshall, 28, set fire to the victim's one-bedroom bungalow to cover up the killing, jurors were told.
For nearly two years, Mr Fasoli's death was put down to an accident until his family discovered footage on his computer hard drive.
His nephew Christopher Murgatroyd examined his fire-damaged computer out of curiosity in November 2014.
Expecting to find research on his family tree, Mr Murgatroyd was horrified to find himself watching his uncle's violent death, jurors heard.
Prosecutor Edward Brown QC warned jurors the attack was "as shocking as it was determined" before playing extracts of the video which went on for six hours.
The defendant first got in contact with Mr Fasoli through gay social networking site Badoo in December 2012 and offered to set up a threesome, the Old Bailey heard.
Marshall arrived at the victim's home at around 7pm on January 6 purporting to be a law enforcement officer kitted out with a police utility belt, handcuffs and a pistol holster, the court heard.
The victim was 'visibly distressed' and threatened with a large knife
During sexual role play, Marshall stripped the victim and arrested him for "being a spy" and hacking into a government laptop, the court heard.
The footage showed Mr Fasoli become visibly distressed as he was gagged and bound on his bed.
He was threatened with a large hunting knife and forced to hand over his cash card pin numbers, the court heard.
Marshall muttered "suspect detained" after injecting him with a drug to "put you to sleep while I go to the cash machine", jurors heard.
The victim then screamed that he could not breathe and began to "squeal" as Marshall clamped his hand over his nose and put his arm around his neck, the court was told.
The pair struggled together on the bed and Mr Fasoli shouted out "No, no, please!" when Marshall produced a roll of cling film and wrapped it around his face.
Marshall, who was shown in the video wearing latex gloves, then held a plastic bag over Mr Fasoli's head, jurors were told.
Afterwards, the defendant spoke into his radio saying: "Oscar one, from papa four, ready for transport, over," jurors heard.
'There is no emotion, no panic, no regret'
Later, the victim could be heard gurgling as Marshall checked for a pulse and spoke into his radio, allegedly saying: "Urgent ambulance required at my GPS location... yeah that's lack of oxygen and can I get them with a crash trolley please."
Mr Brown said: "Obviously there was no real radio connected to anyone, let alone an ambulance.
"There is an ominous determination and seriousness in the way the defendant is carrying out the task, as he sees it. There is no emotion, no panic, no regret."
As Mr Fasoli lay dying on the floor, Marshall allegedly stood and "calmly" lit a cigarette then made the sign of the cross and recited a blessing for the departed in Latin - Patris et Filii et Spiritus Sancti - and the word resurrection.
When the visual flickered off, the audio continued as the defendant tidied up, jurors heard.
Restraint and asphyxia 'contributed to his death'
At 12.41am, the sound of a cigarette lighter being flicked could be heard before footsteps leaving the flat.
The crackle of flames taking hold and a fire alarm were also caught just before the recording ended.
After he fled the scene, Marshall sent a "calculated and cynical" message to Mr Fasoli on the Badoo chat line apologising for not seeing him the night before.
He allegedly withdrew £400 in cash from the victim's bank and used his card to buy a flight to Rome.
A post-mortem examination initially gave the cause of Mr Fasoli's death as inhalation of fire fumes.
A re-examination found he was still alive when the fire was set but restraint and asphyxia also contributed to his death, Mr Brown said.
Marshall, of East Ham, east London, denies murder. The trial was adjourned until Tuesday (August 1).
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