HE was the Scots director behind some of the quirkiest and best-loved films of the post-war period, including Whisky Galore and The Ladykillers.

But despite a glittering career spanning London and Hollywood, the late Alexander Mackendrick never succeeded in getting his passion project about Scotland's most famous monarch off the ground.

Half a century after being sidelined, however, Mary Queen of Scots will be given its world premiere on BBC Radio 4 this Saturday, directed by award-winning Edinburgh-based filmmaker Hope Dickson Leach and narrated by Glenda Jackson.

The title role in the drama is played by rising star Ellie Bamber - girlfriend of Renfrewshire-born Bodyguard star Richard Madden – alongside a host of Scots acting talent that includes Bill Paterson, Mark Bonnar, Kevin Guthrie and Emun Elliot.

The action takes place over a tumultuous 15 months as the young Scottish Queen, isolated, pregnant and betrayed, must fight for her place and try to overcome the warring and manipulative men that surround her.

Like so many of the protagonists in Mackendrick’s films, which also include The Sweet Smell of Success and The Man in the White Suit, Mary Stuart is depicted as a person of drive and steely intelligence.

Indeed, it was this intelligence that first attracted Ms Dickson Leach, writer and director of acclaimed 2016 film The Levelling, which won a Scottish BAFTA, to the piece.

“What really drew me in was the thought of this very young woman in the middle of all these machinations of power,” she says. “She’s got so much responsibility and, on the surface, so much power. But is the power really hers to have? How does she take back the power? How does she become powerful? These were the sorts of questions that really interested me.”

Mackendrick, who died in 1993 aged 81, had originally envisioned Mary’s story as a western, a battle between rival clans, but also described it as “a gangster study”. The project was deemed too disrespectful of royalty in the 1950s, and the director later worked on the script with writers Gore Vidal and Anthony Burgess. The film was eventually scheduled to go into production in 1969.

But after Mackendrick, who was born in Boston to Glaswegian parents and moved to Glasgow aged seven, accepted a teaching post in the US, it was never made.

Ms Dickson Leach describes the script as “simply fantastic” and believes Mackendrick aficionados will find much to enjoy in this 90-minute BBC radio drama.

“The wit is there, the dialogue is very funny in parts and the characters are really well drawn,” says the 42-year-old. “They’re bright, sparky characters who constantly drive the plot.

“Mackendrick was all about characters who want something badly and push on through, even if they are not particularly likeable. Even then, you can’t take your eyes of them. And Mary is very much in that vein. She moves through all the events of this drama and by the end she’s pretty broken – but sees through everything and realises she can never be a player, she will always be a pawn.

“The gender politics are interesting and horrifying. She has to keep seducing her husband in order to keep him onside, at the behest of all these men who are trying to kill her and her lover.”

Mary Queen of Scots, who was beheaded in 1587 on the instruction of her cousin, Elizabeth I, remains one of the most seductive figures in history, as the number of films, plays and books still being written about her highlights.

A major film starring Saoirse Ronan and Margot Robbie is due for release in January 2019. Last year, meanwhile, a critically acclaimed play at the Royal Lyceum in Edinburgh, Glory on Earth by Linda McLean, reimagined the meetings between the young monarch and John Knox.

Ms Jackson, 82, the BBC radio play’s narrator, twice played Elizabeth I, in the 1970s. Following 23 years as a Labour MP representing a constituency in London, she recently made a successful return to acting.

Ms Dickson Leach, who is currently working on a film with actor Jack O’Connell, described her as “incredible”.

“I’m not sure anybody really directs Glenda – she just so amazing and knows the story better than anyone,” she added. “She was also incredibly helpful. She’s a legend and an inspiration.”

The director is also full of praise for 21-year-old Ms Bamber.

She said: “Ellie was phenomenal. She really stepped up to give a beautiful performance. Because this is very much Mary’s story, you’ve got to be able to get behind her."

Unmade Movies: Alexander Mackendrick's Mary Queen of Scots airs on Saturday December 8 at 2.30pm, on BBC Radio 4.