Television audiences may have a bit of a jolt when they tune into Gunpowder, Treason and Plot, Jimmy McGovern's consuming drama about the Stuarts.

For within seconds any comfortable familiarity with Blackadder's Lord Percy or the weaselly Captain Darling are swept away by Tim McInnerny's menacing presence as Lord Robert Cecil.

"It's funny what you get known for as an actor," says McInnerny.

"I loved Blackadder, and we had a ball making it. I'm really proud of the series, but bizarrely, I've spent the minority of my time in comedies."

A polite understatement from an actor who has terrified television audiences as Eric, the paranoid schizophrenic in Trial and Retribution and has cavorted as Frank 'n' Furter in the hit musical The Rocky Horror Show in London's West End.

His work on stage embraces all the classics, including the title role in Hamlet at the Royal National Theatre: "A great role to play. You get all the psychological complexity and he gets to tell great jokes too!"

Pop fans will remember McInnerny in Westlife's Comic Relief video, Uptown Girl.

Cinemagoers enjoyed his appearances in both of Disney's 101 and 102 Dalmatians films and in Notting Hill with Julia Roberts.

"Julia was lovely and very professional," says McInnerny, adding that she knew all the names of the crew within three days - a feat he still hadn't mastered by the end of the shoot.

His latest feature, The Emperor's New Clothes, with Ian Holm, is currently showing nationwide.

"I've been lucky in my work, but when something like Lord Cecil comes along - it's fantastic. You don't often get scripts this good. Frankly, it's the best script I've read in the last ten years, and I can tell you I was desperate to get the part."

Director Gillies MacKinnon and McInnerny talked at length about how to approach Lord Cecil, but ultimately were led by the script.

"I'd read a certain amount, various background books but more really to get a feel and sense of the period. It was an interesting time and I wanted to get into the mind-frame of that world."

But he cautions a pragmatic note: "If we were being entirely historically accurate, then I would never have got the part in the first place, because Cecil was an extremely short man, who was also a hunchback.

"There comes a point, particularly when making a drama set in a contentious period in history, when you follow the script.

"Historians themselves don't agree on what 'the truth is' about these extraordinary times. The victors have so often written history; so who knows?

"It's Jimmy McGovern's personal interpretation that we have to take on board.

"One of the things that really impressed me with his storytelling is that it is not biased. He doesn't come down on the side of Catholics or Protestants or the King."

McInnerny warms to his theme.

"Everybody's a fascinating character for one thing. I've very rarely read a piece that's got something like 15 characters.

"They all have their psychological reasons for why they do what they do, and watching them we see how they are all totally driven by their beliefs. It's Jimmy's exploration of different forms of fanaticism."

He describes the power duel between the ruthlessly manipulative Privy Councillor and the King as a separate story, unravelling behind the thrust of the Gunpowder Plot.

"I see Cecil as the first modern politician, a man who had a vision of England and Scotland as a single state.

"The fanatic within him would die for this abstract idea - he would do what ever it takes to preserve the state. It must grow as a mighty power. The State is his only love and is embodied in the legacy of Elizabeth I.

"The end justifies the means as far as Cecil is concerned and James is his best bet for keeping the country together. That's why he trains and grooms the new king in politics until, ironically, James doesn't need Cecil anymore."

McInnerny says doing this kind of work is the reason he enjoys acting. "It's the nearest thing I've done on telly or film to Shakespeare on stage."

McInnerny's next challenge is set very much in the present, although once again it's the murky world of high level intelligence-gathering and spies. He is the new face in BBC ONE's acclaimed thriller, Spooks.

Audiences can look forward to being frightened by Oliver Mace, an old adversary of Harry's.

"Who is…" and McInnerny laughs, "…a ruthless manipulator consumed with ambition. I must be getting quite good at them."