Man of the moment: Alexander Hanson is set to star in Andrew Lloyd Webber's musical about the Profumo affair

The little known actor will play Stephen Ward, the society osteopath at the heart of the Profumo affair. It's strange becoming a star at 52, he tells Louise Jury

Alexander Hanson is used to flying under the radar. He is an Olivier-nominated actor and singer who was in the original cast of We Will Rock You, saved the day by stepping in to The Sound of Music last-minute and wowed Broadway in Stephen Sondheim's A Little Night Music. Yet he is scarcely a household name.

Instead, it is his wife who everyone recognises. Samantha Bond, with whom he has two grown-up children, has always been the more famous half of the couple, as Miss Moneypenny to Pierce Brosnan's James Bond and now part of the Downton Abbey set as Lady Rosamund.

If the contrast dents his ego just occasionally, he's too grounded to be bugged and comparative anonymity suits him. "I quite like being under the radar," he says.

"There are times when I think, if I were a bit more famous, life could be easier in terms of work because producers want bums on seats and they're going to get bums on seats if they get a name, if you have had that series on telly."

But it amuses him that his evident talent throws theatre bosses a googly. "I quite enjoy the producer's dilemma: 'We should really get so and so– but sadly he can't sing.'" And he has seen enough of fame close-up to identify the dangers. "Once you become famous, you can't become unfamous," he says, adding: "You can become a failure."

Yet he is now preparing to step out of the shadows big-time as the star of Stephen Ward, the new Andrew Lloyd Webber blockbuster about the society osteopath/alleged pimp at the heart of the Sixties Profumo scandal.

Hanson was playing Pontius Pilate on the last arena tour of Jesus Christ Superstar when Lloyd Webber invited him to work on his planned new show with lyricist Don Black and Christopher Hampton, who has written the book. "I was completely blindsided. I was flattered and thrilled and excited."

He admires Lloyd Webber. "He's done exceptionally well and the Brits don't like that much. He's brilliant at writing commercial music." Almost without thinking, he quotes a line from Noël Coward's Private Lives – "The strange potency of cheap music" – and then quickly makes clear that isn't meant to be rude, explaining: "The way it gets under the skin annoys some people."

But he admits he tried to play things "exceptionally cool" over the invitation, not least because involvement in the development of a musical certainly does not mean an actor gets to star in the end result. "They pick your brains and then get Hugh Jackman or John Barrowman or Michael Ball – who are all fantastic," he says. "It wasn't a given." But it was this time. With Stephen Ward, Lloyd Webber has admitted wanting to write a show with an older man, not young women, at its heart. And as the title makes clear, it makes Ward "the motor of the piece".

Hanson's research for the role revealed Ward was an osteopath so brilliant his osteopathy manual is still in use. But he is remembered as the man who introduced Tory minister John Profumo to showgirl Christine Keeler. When Profumo lied about their affair, the politician was forced from office in a chain of events that eventually brought down Harold Macmillan's government too.

Charged with living off immoral earnings and – in Lloyd Webber's view – scapegoated by the establishment for the embarrassment caused, Ward took an overdose of pills and was in a coma when found guilty. Three days later he died.

Hanson is trying to find the characteristics they share to play him. Watching the actor – all smiles and openness and twinkly eyes, despite the spartan surroundings of a downstairs theatre dressing room – I suggest charm seems the most obvious. Perhaps, too, a youthful man's enjoyment of young company.

"He always had a bevy of young girls and he loved young girls, though not necessarily to have sex with," Hanson agrees. "He just loved having them around. He loved the chaos of them." And of course, pretty young girls proved part of Ward's ticket to success in high society where he mingled with aristocrats, film stars and power-brokers – until the scandal hit.

Hanson says it's "lovely" to be sharing the stage with Charlotte Spencer, who plays Keeler, and Charlotte Blackledge, who is making her professional stage debut as Rice-Davies, though admits it is strange that the young cast are the same age as his 22-year-old daughter, Molly. "There's that confusing thing about being a lustful old goat and being quite paternal – thinking they need looking after," he laughs.

And curiously the show draws on childhood memories for him by recreating Murray's nightclub, the Soho joint where Keeler and Rice-Davies were working when they met Ward.

Hanson was born in Oslo – he spoke Norwegian for the first few years of his life – to a half-French, half-Norwegian mother, Ellen, who had divorced his English father very early in their relationship. She remarried a Nottingham businessman, George Akins, who was a bookmaker and ran amusement arcades, casinos and the most famous nightclub in the city, the Parkside Club. "I remember sitting in the club watching the go-go dancers," Hanson says.

His early taste of showbusiness was through his stepfather's friendship with the acclaimed actor John Neville who ran the Nottingham Playhouse and who brought stars – even including Elizabeth Taylor and Richard Burton – to the Parkside. So clubs seem very familiar. "I said to [director] Richard Eyre, I know that world," Hanson says.

Yet on leaving school, the young Hanson was prepared for a career in hotels and catering and spent a year at the Ritz in Paris as a trainee before deciding to follow his heart – and the influence of his gay Norwegian theatre-designer uncle, William Jensen, who always encouraged him when he did impressions. He got into drama school, the Guildhall, at the second attempt. "I thought, 'This probably won't work out. I can always go back to the catering.' But a job would come through just at the right time."

And he has shared his life in showbusiness with Samantha Bond whom he first saw when she was starring in Christopher Hampton's play Les Liaisons Dangereuses. "I thought she was all right," he smiles. By the time they were an item, she was playing Beatrice to the hotshot Kenneth Branagh's Benedick on stage in Much Ado About Nothing in 1988.

"And when I first moved to her flat, the phone was ringing the whole time, people wanting the talent of Sam. It was quite a lesson living with the missus to start with. It was all about her. But I fancied her rotten and I loved her."

Their two children, Molly and Tom, have long been the focus of their lives. "We needed to work but if we could do good work, that would be a bonus," he says. But now Molly is studying drama at Bristol University and Tom's at Rada, both following in their parents' footsteps, he and "Sam" are empty-nesters and a different kind of world awaits – a new potential blockbuster in the West End.

"The great thing about this game is I'm 52 and I've just got the lead in the West End. That's kind of cool," he says. And with a rare flash of ego, he adds: "It's a real thrill, a little bit of finally being first choice."

'Stephen Ward', Aldwych Theatre, London WC2 (0844 847 1712) in preview; opens 19 December