King Lear by William Shakespeare at The National Theatre Director Sam Mendes Designer Anthony Ward Lighting Designer Paul Pyant VIdeo Designer Jon Driscoll Fight Director Terry King Music Paddy Cuneen Sound Designer Paul Arditti Cast Stephen Boxer Cassie Bradley Tom Brooke Richard Clothier Jonathan Dryden Taylor Paapa Essiedu Kate Fleetwood Colin Haigh Simon Manyonda Anna Maxwell Martin Daniel Millar Michael Nardone Gary Powell Simon Russell Beale Adrian Scarborough Hannah Stokely Stanley Townsend Sam Troughton Olivia Vinall Ross Waiton

It’s almost disconcerting hearing Simon Russell Beale (pictured) purr like a bear on the phone as we discuss one of the biggest roles of this Shakespearean giant’s life. This, having just the day before watched his towering performance as the mighty King Lear whose descent into madness is played out for everyone to witness.

It is the extremes of emotional heft that’s overwhelming to watch. To play that kind of role where you’re moving from maddeningly majestic to madness must be quite terrifying – night after night.

But Russell Beale on first acquaintance sounds a very solid kind of man. He also has the security of having worked with the director Sam Mendes since his 20s with this their ninth show together. This latest King Lear is now in his early 50s and he thanks his lucky stars that he didn’t turn down the role of the clown in Troilus and Cressida, which Mendes first offered to him. “I also remember it was an extremely good cast with Ralph Fiennes as Troilus,” he lets slip.

“At the time, he was the new kid on the block and I wasn’t happy to be given the clown’s part,” says Russell-Beale, who only a few years earlier while busy with graduate studies hadn’t yet settled that he would become an actor. It was the buzz around this new director though that appealed to him and pushed him to take the part.

Now they’re like two old shoes when working on a play. “We don’t see much of one another between plays, but every two years or so, he calls me up,” says the actor.

King Lear must be one of the most daunting roles for any actor but Russell Beale knew it was time. He and Mendes had been speaking about it for two years so at least he had a chance to get used to the idea. And when you ask him about the interpretation, there are obvious things that he worked on before, but the performance only comes into play when working with the other actors.

“I have to react to the way my daughters interact with me,” he says about his character. And when you see the play, it will make even more sense.

He does admit that Mendes wanted him to shave his hair. Usually he has a floppy mop that now has a very distinct silver shine. “I have had to shave for him the last three productions, so he obviously prefers it this way,” he chuckles.

But he gives the impression that these are minor details that add to building his character.

Mendes tells a very innovative tale in his King Lear. This is Shakespeare’s story, with not a word changed, but the director has a vision that plays well at this time with a cast that serves him well.

One of the things that Russell Beale did research was dementia and more specifically ageing dementia. “It’s quite clear that he suffers from something,” he says. And because he has family in the medical field, this is where he sourced his information.

“It’s the wandering, the hallucinations,” he says that take you down that road. It also informed his playing because once he knew more about the symptoms, these were things he could add to his performance – the shaking hand for example, which he describes as very useful. “I found it grounded my performance from the start.”

It’s also the approach towards the end that adds weight to not only the madness but also the tragedy of our times, ageing. So few people are prepared and the children are often cruel in the way they behave simply because they don’t have the skills to deal with this novel situation.

Apart from the power, greed and other obsessions that come into play, this adds to the tragedy of Lear’s degeneration as he disintegrates not only because of his mind but also because of his heart – perhaps. This is someone who has never had anyone say no to him before.

“He wasn’t a very nice man,” says Russell Beale of the king.

But he has empathy as his life starts to unravel and the performance captures all of that.

On a practical level, playing King Lear has been extremely demanding.

“I was aching all through rehearsals,” he admits but he had built up the stamina even if the run has almost run its course.

“I think I have put a full stop behind this one,” he says of his performance.

When he played Hamlet, he felt he had done as much as he could but there was also unfinished business. Not this time round. And then he stops the conversation: “But listen, I’m playing King Lear at the National, it takes my breath away when I remind myself.”

And how wonderful to hear an actor so enchanted speaking about his dream when he is playing one of the biggest roles on one of the biggest stages in the theatrical world. The performance is that big too.

Don’t miss it and if you happen to be in London in the next few weeks, it’s running until July 2.