Jimmy McGovern's Gunpowder, Treason and Plot is a four hour epic for BBC TWO, which tells the stories of Mary, Queen of Scots and the extraordinary victory of James I of England over the Catholic conspiracy that tried to undo him.

Writer Jimmy McGovern recalls: "When BBC Television first asked me to write the story of James I and the Gunpowder Plot, I was already writing about his mother, Mary Queen of Scots, for BBC Northern Ireland.

"So we decided to combine the two and show them both as television films and the result is Gunpowder, Treason and Plot."

For McGovern, the biggest challenge in writing a historically-based drama is the reactions of some historians.

He acknowledges: "The historians will put the boot in, of course. They hate historical drama. It simplifies things, you see.

"The dramatist cannot say, as historians say, 'On the one hand we can assume that Mary Queen of Scots had her husband killed because she was in love with another man. On the other hand, she might have been totally ignorant of the matter.' That would make a nonsense of the drama.

"Characters in a drama have to have clear motives. The dramatist chooses those motives as fairly and as honestly as he can. And then he sticks to them. Unlike the historian, he cannot hedge his bets.

"Nor does he have the luxury of the footnote, or the appendix. The historian can rip off all those historians who have gone before him and then simply acknowledge their work in a footnote. The dramatist cannot do that.

"I have written history before. Sunday was about Bloody Sunday in Derry in 1972. Hillsborough was about the 1989 football disaster and Dockers was about the Liverpool Docks' Dispute of the mid-Nineties.

"But the people affected by those events are still alive; so I did not dare to take any liberties with their stories. I could not impose clarity or simplicity upon them. The truth, no matter how messy or complicated, had to be told.

"Writing about the early Stuarts is much easier. They have been dead for 400 years. Nobody is going to get hurt by what I write. And nobody knows the truth.

"That is why there have been so many books written about Mary and James I, each contradicting the one that went before.

"Nobody knows the truth. There are some established facts, of course.

"Mary, for example, did marry Lord Darnley and he was undoubtedly murdered, then Mary married the man suspected of that murder.

"As for James, there is no doubt that Catholics did try to blow him and his parliament to bits.

"And where the facts are established, I have stuck to them throughout my drama.

"But where there is room for embellishment, I have embellished. That is what a dramatist does. That is what Shakespeare did. And if it was good enough for him, it's more than good enough for me."

The challenges of bringing the drama to the small screen were equally demanding.

Producer Gub Neal, who has worked with Jimmy McGovern for more than ten years, admits that this was their toughest show yet.

Neal says: "We were lucky to have acquired a brilliant director.

"Gillies MacKinnon had fantasised about doing the Stuart story from a very young age. Gillies had also directed Jimmy's debut film 12 years ago, Needle, and although they had always wanted to team up again - it hadn't yet happened. The auspices were good.

"Gillies brought a terrific creative team with him, which together with Willy Wands our co-producer made for a formidable crew.

"To be honest we were going to need the very best people because we were about to attempt something extraordinary.

"Most television 'costume' dramas are shot on National Trust property within the British Isles.

"They are invariably adaptations of romantic novels which, whilst worthy of translation, do not attempt battles, explosions, coronations or multiple public executions.

"Our stories were bloody, epic tales, involving courts and castles, not to mention mobilising vast numbers of costumed extras across muddy planes.

"To make one of these films alone would have been hard enough but to try and make two of them, back to back, was obvious madness.

"They required 800 hours of filming, 66 principal characters and 12 major sets in just three months of production.

"Fortunately, none of us bothered to stop and think too hard about what we were doing.

"It's a funny thing about production. There is a collective pathology, or even psychosis, that joins the cast and crew early on in the process and promotes the essential delusion: 'well we are doing it so it must be possible, mustn't it?'.

"But a bit like a cartoon character who has overshot the edge of the cliff, one just has to avoid ever looking down.

"Gillies was really our high priest in this process. Inspiring actors and crew alike.

"He invested every corner of the production with a sense of possibility. Never afraid to change his mind at the last minute, of course, he would lunge for what seemed best.

"Through it all he directed the films like a firecracker at the Edinburgh Tattoo. I have no idea where he got his energy.

"And Andy Harris, our Scottish designer, led an army of construction crews in recreating the major landmarks of Scotland and England in a Romanian studio, and they were a massive undertaking.

"There was the Edinburgh street, the Palace of Westminster, the Scottish castles, the English castles, the taverns, the cellars, and the churches.

"But the sets weren't handicapped by history or modernity. No clipped lawns or tea rooms to hide, street lamps to cover or satellite dishes to spray grey.

"Andy had free rein to plaster his world with pig shit, to chisel dirt and debris into the walls of his Scottish castle in a way that the curators of English Heritage or the National Trust for Scotland would interpret as vandalism!"

Yet, for Neal, it was a project well worth all the time, the patience and the energy: "Jimmy's writing isn't just history, it's drama of the highest order.

"His writing, especially when one considers titles like Cracker, Priest or Sunday, is essentially Jacobean.

"Ironically, both these stories were quite literally set in the period that gave birth to that genre.

"Here, all the familiar themes of McGovern's work could resonate, coalesce and perform their special magic; intrigue, corruption, power, sex, religion, redemption and vice.

"For Jimmy I think the history of a great Queen and a great King provided the perfect legendary setting for two very different morality tales.

"The stories themselves explore the theme of power and kingship, but also demonstrate a reversal of fortune that shows that emotion will undo power, as easily as power will undo emotion.

"For Mary's quest is halted and faulted by her love of Bothwell, whereas her son James succeeds where she fails because he learns that to show love, mercy or compassion is a weakness.

"If there is a universal truth to be drawn from Jimmy's writing and Gillies direction of these stories, it is that the human condition is very delicate and that to achieve a balance between love and control is never easy.

"The grace and beauty of Mary's journey is an inspiration, because in spite of her fallibility, she sacrifices herself to save her son, her lover and ultimately to save her kingdom.

"She starts from a position of power and ends up imprisoned, but somehow we suspect that her soul is safe.

"James' journey is more jagged, and much darker. He captures the prize that eluded his mother's grasp, and in some strangely twisted way he did it all to justify his mother's love.