He crossed into the eastbound lane and continued to drive on the wrong side of the road to the crest of a blind summit. Witnesses estimated Macpherson’s car was travelling at about 65mph. The speed limit was 60mph. 

Advocate depute Alan Mackay, prosecuting, said the Corsa left the road and rolled onto its roof after the crash. 

“The engine ignited enveloping the front of the vehicle in flames. The three occupants were trapped,” he said. 

“The Honda slewed round and came to rest on the carriageway facing the south verge. Again, the occupants were trapped.” 

A nurse who stopped to help saw Mrs Melville and her son were dead. Mr Melville snr was unconscious and died later in Perth Royal Infirmary. 

When police arrived, they pulled Macpherson, whose legs were on fire, out of the burning Corsa but were unable to save his female passengers, who were from Crieff. 

Mr Mackay added: “The bodies of Tanya Webster and Donna Miller were on the back seat of the car. Because of the intensity of the fire and the heat it was impossible, at that stage, to retrieve them.” 

DNA tests were needed to establish identities.

A post mortem found all victims had died from multiple injuries as a result of the crash.

Macpherson suffered a broken arm and severe burns to his legs.

He was in hospital for several months and police were only able to question him about the accident last May. Lord Brailsford, who called for background reports, told Macpherson that he now faces an “almost inevitable” prison sentence.

The judge allowed Macpherson – a first offender – to remain on bail, but took away his driver’s licence.

Lord Brailsford said: “Patently, this a tragic case. It is difficult to imagine a more tragic case.” 

Defence QC Peter Gray said he would give Macpherson’s side of the story when he returns to court to face sentence in May.