“COMPLETE passion, utter dedication, inspiration, hard work — she said the rest was kakapeepeedoodoo.”

With such delight did actress Stephanie Beacham give that last word construction to me talking about her role as opera diva Maria Callas.

I’d asked about the essential elements in Callas’s character to grasp as she prepared for Master Class, coming to the Playhouse next week. Without lingering on the matter, the “doo-doo” part of the word gives the game away: Callas was driven professionally — all else was rubbish.

The conceit of this 1995 play is that Callas, retired in the early 1970s, is teaching three aspiring singers at New York’s Juilliard School and, as she discovers faults in them, exposes her own life to them.

“She was an incredibly difficult person,” says Beacham, “one of those high achievers and someone who is damaged goods — fascinating, diva, damaged goods. Follow it through and you’ll find a difficult childhood.

“The more damaged you are, the more protective you have to be of yourself, and people with very high standards are misunderstood by those more ordinary.”

The great sadness in the life of Maria Callas came when Aristotle Onassis left her for Jackie Kennedy. She never recovered from the blow, but there was more.

“It wasn’t the first time. She had, as the Americans would put it, abandonment issues earlier than that because of the break-up of her parents; there was almost an inevitability in psychological terms that she wouldn’t get over the Onassis horror.”

Although there are other characters in Master Class, they are effectively props — there solely to listen to Maria Callas’s outpourings.

“I prefer bouncing off other actors. I hadn’t realised quite what a lonely business it was going to be. I was talking to Faye Dunaway about it the other day because she did it for ages in America.

“It can be quite lonely and all the energy has to come from you: you’re having to be the fireworks and the volcano! So, it’s a job of work, all 10,486 words of her!”

Driving a drama is nothing new to Beacham. She started her career playing kittenish parts in The Saint and Jason King — and her topless scene with Marlon Brando in the 1971 film The Nightcomers may be remembered by some — but it was as the fearsome Sable Colby in The Colbys and Dynasty that she ensured her TV fame.

She dropped another name seamlessly: “Charlton Heston used to say to me on the set of The Colbys, ‘no one need do anything on the screen when you’re around because you’re doing it all for them’.

“Acting ‘big’ was appropriate for that kind of stuff! If you look at the greatest actress, probably, of our time, Meryl Streep, she doesn’t act small either.”

I wondered if, in those glitzy American series, she or any of the other leads had any input into character or plot development.

“Not much. But I remember when I first went on, they had me undoing the girth on Barbara Stanwyck’s horse so that she would fall off!

“But I realised Sable didn’t need to do this: she didn’t need to do physical things of that sort but could do it mentally or vocally. So, undoing people by honeyed tones. Much more interesting,” Stephanie rounded off with a catlike purr.

Throughout her career, Beacham has had to deal with the fact that she is deaf in one ear.

I asked whether this had really affected her professionally?

“I don’t know, because I never had proper hearing; it’s not as if I’d had it and lost it.

“But whenever I come to a new theatre, I have someone be at the back and let me play vocal games so that I get a good understanding of the size of voice required.

“I don’t need help; I need to work harder at it.”

Stephanie Beacham’s never had such good reviews in her life as she’s having for her Callas.

She’s clearly working at it very well.