“Go on, tell me more about him!” So jokes Simon Ward, star of the new touring version of Alan Bennett’s The Madness Of George III when Nigel Hawthorne’s Bafta Award-winning performance on stage and screen is mentioned.

“Someone passed me Alan Bennett’s memoirs and I looked up Nigel Hawthorne’s name in the index,” says Simon.

“Alan said he gave the most superb, wonderful performance, that he was brilliant and marvellous.

“I put the book down and thought, ‘Oh God!’”

It hasn’t put the star of Zulu Dawn, Judge John Deed and All Creatures Great And Small off the role, though – in fact he admits he is looking forward to the challenge.

“One of the lovely things about the play is that all the parts are quite superb,” he says. “It will be challenging for everyone – you’ve got to have a team which is unselfish.

“It is an incredibly complicated play, physically and mentally. I don’t think I know a play that entwines tragedy and farce in such an extraordinary way.”

The play tells the story of King George III’s battle with mental illness, as his son, the portly Prince Regent – creator of Brighton’s Royal Pavilion – tries to take his throne.

“All our attitudes to mental illness have changed, but they are still pretty old-fashioned,” says Simon in a break from a make-up session based around some of the strange 18th century methods employed to try to cure the king.

“I think we are still frightened by it – it’s not a quantifiable disease, we still don’t fully understand it.”

As for what sent the king mad, Simon doesn’t think it can wholly be put down to porphyria, which is hinted at in the play through the examination of the king’s dark urine.

“He had porphyria, a blood condition which seemed to be a trigger, but would he have gone mad anyway?” says Simon.

“He was particularly obsessed with losing America and the war of independence.

“I’m trying to be as honest to the illness as possible. All you can ever do when you’re playing a character that actually lived is to try to be as honest and as truthful to that character as you can.

“However, the whole thing about truthfulness in the theatre is all such b*******.

We are just chaps and chapesses dressed up. It always changes – I’m sure people saw Henry Irving and called it a wonderfully realistic performance. The way I describe it is you have to find ways of doing it that are close to our received opinions of how you should play a real-life character.”

Despite the fact his ancestors had been brought into England from Germany, Simon believes George III was genuinely loved as a monarch.

“George III spoke English, and would only speak English in court at all times,” says Simon.

“At the point when the play is set he would have been looking across to France where Madame Guillotine was at work.”

Simon isn’t an avowed republican himself.

“I can’t see any acceptable alternative to monarchy,” he says. “They are all unpleasant. We have been blessed by a Queen who is a remarkable woman by any standards - she’s been like a rock for 60 years, and it won’t be quite the same when she goes. She has defined an era.

“She has got a popularity similar to George III, who had a huge raft of problems up against him. It’s not easy being King!”

* Starts 7.45pm (2.30pm matinees on Wed and Sat), tickets from £13.50, call 01323 412000.