Belinda Lang and Jonathan Coy talk ahead of Duet For One roles at Wolverhampton Grand

“Mostly it is universally human,” reflects Jonathan Coy, who swaps his Downton Abbey role as a solicitor George Murray to play Dr Feldmann. “This woman is confronting a life-changing problem with sarcastic humour and resisting all the efforts of the psychiatrist to get her to look deep into herself, which she refers to as psychobabble. But it is a sparring relationship and that is where the humour and wit spirals from.”

And while Jonathan is new to the role, his sparring partner is not: Belinda Lang (best known for playing Bill in TV’s 2 Point 4 Children) is reprising her role as Stephanie Abrahams, the brilliant concert violinist who seemingly has it all but who is forced to re-evaluate her life when tragedy strikes.

“It was very hard to rehearse but actually doing it in front of an audience is very satisfying,” says Belinda. “He [Tom] uses a violinist as the protagonist, and she is supposed to be depressed, but fundamentally it is about someone who is angry and who doesn’t want someone else delving about in what she sees as her private world. There are moments in the play when pain hits, but it doesn’t dwell on it. It’s a much funnier play than I thought it was and it is very reassuring in that way,” she adds. “I suppose what you really get from it is how fantastic human beings can be for each other. This relationship that starts off so badly gradually becomes so supportive, but in a way that seems more real to me.”

Certainly she has seldom received so much audience feedback from a play.

“People really respond,” she confirms. “They write and come to stage door because of the humanity; it speaks to them about themselves.”

Based on the life of world renowned musician Jacqueline Du Pré, Duet for One premiered at the Bush Theatre in 1980 and has since enjoyed several revivals, as well as a 1986 film adaptation that saw Julie Andrews nominated for a Golden Globe for Best Actress. Extending the tour following the play’s successful run last year, Producers Lee Dean and Daniel Schumann have appointed Robin Lefevre as the play’s director, but as a two-hander it is down to the actors to summon the absolute focus required. With nowhere to hide, Belinda admits she takes a very deep breath before each performance.

“I always say ‘please let me sustain the energy!’ But that’s where you can tell good writing. This play is like a sea with a lot of salt in it – the writing supports you. It has this trajectory that really is splendidly written.

“It is very bright and alive, but the main attraction is that it does that thing that theatre does so well in that it approaches a universal humanity and finds an extreme metaphor: a concert violinist who knows that she will never play again,” explains Jonathan, adding that the duel between the characters’ razor-sharp minds is a life-affirming tribute to the human spirit.

“The most important thing in her life has been taken away and that is so relatable,” he says, admitting that he also jumped at the chance of working with Belinda again.

“That was definitely part of the appeal,” he chuckles. “We have been friends since we were in our twenties and we have done a couple of shows together. Spending a few weeks on tour with her is no hardship at all.”

Talking of touring, is Jonathan a sightseer – are the guidebooks already marked up with places of interest in preparation for the tour?

“I do try to make the most of wherever I am. Belinda and I are the last generation who learnt our trade in regional theatre reps, so I think regional theatre is very important, but it’s always a joy to visit somewhere new. I’ve seen the world but never bought a ticket, as they say. On this tour they are all places that I don’t really know; virgin territory that I am looking forward to discovering.”

“I’m not very good at being idle,” confesses Belinda. “A short tour of say nine-ten weeks is fine, but it all takes such a lot of planning. I can’t bear to leave anything to chance and you do get more anxious as you get older. I’m always asking myself if I am on the right train or if I have got the address for the digs. But Jonathan and I are old friends, so what’s not to like?”

“I haven’t been to Wolverhampton for so long that I’m looking forward to rediscovering it,” says Belinda, who likes to have another project bubbling in the background that she can tinker with on tour.

“I translate plays from French and adapt them, and I do like to walk wherever I am. I find walking very relaxing.”

With Jonathan coming to the play for the first time and Belinda reprising her role, which is the bigger challenge?

“I’ve done it once before, so that gave me a lot of perspective,” says Belinda. “This time, having done it at end of last year, the advantage is that it is fresh. The disadvantage,” she paused, a broad smile forming, “is that it was just long enough ago to have forgotten the lines!”

Two superb actors, an ace director and brilliant play: this ‘Duet’ will be pitch-perfect in every way.