Alexander McKellar, 31, was driving the vehicle at high speed under the influence of alcohol when it struck 63-year-old former navy officer Anthony Parsons late at night on the A82 near Bridge of Orchy, Argyle and Bute, in September 2017.

He then covered up the crime for more than three years with the help of his brother Robert, who was in the passenger seat.

The High Court in Glasgow heard how both men fled the scene before returning in another vehicle and later burying Mr Parsons’ body in a shallow grave on the nearby Auch Estate where they lived and worked as farmhands.

But their cover-up was revealed after Alexander McKellar confessed his crime to a girlfriend who then alerted police. He was sentenced to 12 years’ imprisonment after admitting charges of culpable homicide and trying to defeat the ends of justice.

Robert McKellar was sentenced to five years and three months’ imprisonment after pleading guilty to trying to defeat the ends of justice.

Ruth McQuaid, procurator fiscal for High Court, Crown Office and Procurator Fiscal Service (COPFS), said: “These were heinous and calculating crimes which brought untold distress to Mr Parsons’ wife, children, and grandchildren. They were left in the intolerable situation of not knowing where he was or what had happened to him.

“The fact that Anthony’s disappearance was subject to a major missing persons enquiry for several years meant his family were left in the dark over his whereabouts.But all the time, Alexander and Robert McKellar were going about their everyday lives knowing that, in fact, he was dead and that they had buried him amongst animal carcasses.

“They kept this secret with wilful disregard for Mr Parson’s family. Our thoughts are with those who have been affected by the unconscionable and brutal actions of these two men.”