A NEW documentary on the mysterious death of SNP activist and senior lawyer Willie McRae has prompted fresh calls for a public inquiry into the case.

The film-maker Roderick Mackenzie hopes to use the 26-minute work as the basis of a three-part mini-series and has backed demands for a further probe into the event.

Mackenzie was inspired to embark on the project through his late grandfather Hugh Mackenzie, a Highlands’ doctor and independence supporter who knew McRae.

It uses rarely seen footage of the independence campaigner including an interview he gave to the BBC and features contributions from other researchers including by the Justice for Willie campaign.

A leading independence activist and anti-nuclear campaigner, McRae was a thorn in the side of Margaret Thatcher’s Tory government.

READ MORE: Nurse who treated Willie McRae: It wasn't suicide, he was shot

He was the SNP’s Westminster candidate in 1974 and 1979 for Ross and Cromarty and a former vice-chairman of the party who in the latter year stood in the party’s leadership contest, which won by Gordon Wilson.

A fierce critic of the UK nuclear lobby and a key figure in a successful campaign against plans by the Atomic Energy Authority to dispose of nuclear waste in the Galloway Hills in 1980, he was often in the public spotlight.

Controversy has long surrounded the official explanation of McRae’s death aged 61. He was found critically injured in his crashed car off the remote A87 near Invergarry in the Highlands in April 1985 and died a day later.

Police discovered a gun lying near his Volvo saloon. A post-mortem report stated McRae was shot in the head – on the right temple – and that the injuries were “suggestive of suicide”.

However, many believe he was murdered. For more than 30 years speculation has grown that he may have been killed by the security services.

An official SNP inquiry in 1985 led by former party president Winnie Ewing concluded it was not satisfied with the finding McRae took his own life.

An investigation by the Justice for Willie organisation led to campaigners recruiting two high-ranking former police officers to launch a private investigation with them concluding there was “no credible evidence” of murder.

The pair uncovered testimony revealing that McRae had been suffering from depression, drinking heavily and had threatened to take his life. In one instance a close friend entered his home to find him holding a gun and stating that life had become “all too much for him”.

For more than a year Mackenzie researched the story, poring through newspaper reports on McRae’s life and tragic death. He was told about a new witness who may have passed McRae’s crashed car and another vehicle parked nearby.

“[The witness] gave a statement to Police Scotland recently, but had offered it back during the time but had been told then the investigation was concluded,” Mackenzie told The National.

“He apparently had a memory for memorising car plates during journeys and could recognise where they came from, recognising the second car as not from the area and knowing McRae’s car.”

Mackenzie added: “I believe a public inquiry would finally answer some questions, and with full witness statements released and evidence there would be some answers. The Justice for Willie campaign gave some closure and offered a statement that aligned with police rather organically with room for speculation.

“There is only one witness statement really that gives pause for police to investigate, and unfortunately that will be up to the appropriate authority to grant another look into the case.”

READ MORE: Old interview backs up nurse’s suspicions about Willie McRae's bullet wound

Two years after the Justice for Willie inquiry reported its conclusions, suspicion McRae was assassinated surfaced again when a nurse working at the hospital where he died, who said she cared for him in his final hours, came forward to The National to dispute the official finding. Katharine McGonigal contradicted the report the bullet wound was in the right temple and insisted it was at the back of his neck. McRae’s brother Fergus had previously indicated the wound was not in the temple. McGonigal’s account prompted the SNP MSP Alex Neil to call for a public inquiry.

“I would say that Willie McRae’s death has become more important than his life’s work,” Mackenzie said.

“Where he should have inspired people to be anti-establishment with the very real corruption of nuclear dumping and unscrupulous political and business interests of the British government, he is instead remembered as a martyr ... I found no criminality, I found tenuous evidence of suicide and more than a few people who just want Willie’s memory to be at peace.”

The documentary went towards work for Mackenzie’s Masters degree at Robert Gordon University in Aberdeen.

A spokesperson for the Crown Office & Procurator Fiscal Service said: “Crown Counsel are satisfied with the extensive investigations into the death of William McRae and the case is now closed.”