'He’s a compelling figure, but one with a hard, ruthless streak' … Ben Miles on Thomas Cromwell. Photograph: Gareth Cattermole/Getty Images  When Hilary Mantel first introduces us to Thomas Cromwell, the wily social climber at the centre of her award-winning historical novels, he's face down in a pool of his own blood. It's possible to view the entire narrative that follows in Wolf Hall and Bring up the Bodies as Cromwell's defiant rise, as he scrapes himself off the floor and ascends to the zenith of 16th-century politics.  "These plays are about how this man gets up on his feet having been on his knees and how far he goes," says Ben Miles – the actor shrugging on Cromwell's robes – of the Royal Shakespeare Company's pair of stage adaptations, now transferred to London's West End. Cromwell – "the original working-class hero, the original self-made man" according to Miles – is the scheming heart of the two stories, determinedly throwing off his humble origins and charming himself all the way to Henry VIII's side. He's a compelling figure, but one with a hard, ruthless streak.  "Morally, it's very ambiguous," says Miles, identifying this ambiguity as one of the attractions for him as an actor. "People are intrigued, they're drawn in by this charismatic figure who drags himself up, but the means by which he does that are often dubious. There are lots of themes in these stories, but one of them is this idea of vengeance or retribution – how far do you carry that? When you're finally in a position of power, what do you do with that power? Do you use it to settle old scores, or do you use it for the common good? Or do you do both? I think that's what Cromwell finds himself doing. It's an endlessly fascinating study of human character."  Also fascinating is the wider Tudor context, and the fierce debates that still surround figures such as Cromwell, Henry VIII and Anne Boleyn. "I think these plays and these books have really held a light up to that period," says Miles, who confesses to having been a huge fan of Mantel's novels even before the RSC project arose. "Hilary's rewritten the book as far as opinion about Thomas Cromwell is concerned," he adds, describing the experience of bringing this reimagined character to life as "a great thrill".  While Mike Poulton's stage versions of Wolf Hall and Bring Up the Bodies are necessarily "streamlined", stripping out a number of peripheral characters and subplots, Miles insists they remain faithful to the vivid character portraits in the books. "What the plays keep, I think, are the main arteries of the story," he says. And, like Mantel's novels, the plays succeed in marrying historical narratives with a very modern set of concerns and sensibilities.  "Politics, nationhood, religious fervour, extremism, European political machinations, the threat of war, how to get on in the world, the trials and tribulations of the self-made man – all these things, they're things that concern us now and will always concern us," he says. "It's these things that make the plays contemporary, as well as period."  • Until 6 September. Box office: 0844 453 9025. Venue: Aldwych theatre, London
<b>Catherine Love</b>: The RSC actor discusses the moral ambiguity of Mantel's world and the thrill of bringing it to life on stage