Marion McMullen makes the cast and director of theater production Blue/Orange a little nervous before the play arrives in Birmingham next week.

Weve never done this before, admits director Christopher Luscombe with a nervous laugh.

Hes invited me and a couple of other journalists down to London to sit in on rehearsals for Blue/Orange and a peek behind the scenes.

He sounds like hes now having a few second thoughts as he explains: I did something like this for a musical at West Yorkshire Playhouse, but we rehearsed and rehearsed beforehand and we were note perfect. There's no singing or dancing in this ... its just the play.

Even Downton Abbey actor Robert Bathurst is a little nervous about having a journalist watch his every move before the play heads off on tour.

Its not something Ive ever done before, he laughs. No-one normally sees the play before opening night. Im surprised at how nervous I am.

The Cold Feet and Wild At Heart actor also played Dads Army actor John Le Mesurier in Hattie but has currently been finding international TV fame as Downton Abbey widower Sir Anthony Strallan.

Sir Anthony recently broke Lady Ediths heart by dumping her at the church on her wedding day but, as Lady Edith, tries to get over the loss, Robert is keeping busy with Blue/Orange.

He is starring alongside Oliver Wilson and Gerard McCarthy in the psychological thriller centered around a man called Christopher who believes his father is a notorious military dictator.

A junior psychiatric doctor wants to do further tests and plan longer care. But senior consultant Robert wants to thrust him back into the community and a riveting, compelling and witty battle of freedom and ambition unfolds.

Its the best play Ive read in years, says 55-year-old Robert as we sit on the chairs on the hospital set, and it keeps you guessing.

The production is a far cry from filming ITVs Downton Abbey with its lavish costumes and large cast.

The play is a three-hander with a bare set and theres not a corset or bustle in sight.

Instead, the walls at the London rehearsal space near Euston Station are lined with computer print-outs of pop culture and references from the play.

Its a wonderfully engaging play, says Robert, and the audience have to decide what they think of the characters. It is a real character piece.

The multi-award winning play by writer Joe Penhall opens at the New Alexandra Theatre in Birmingham next week as part of a national tour before transferring to Londons West End.

Joe wrote the original play 12 years ago and it won an Olivier Award, a Critics Circle Award and the Evening Standard Award for Best Play

The three-strong cast offer some heavyweight performances. Actor Gerard McCarthy, who plays the young doctor, will soon be seen on screen in Titanic: Blood & Steel alongside Sir Derek Jacobi, Chris Noth, Joely Richardson and Neve Campbell.

While Oliver Wilson, who plays Christopher, has appeared on TV in Misfits, Hollyoaks, Groove Town and Karmic Compensation.

Robert plays the senior psychiatrist, also named Robert, but says there the similarities end. His man management skills are awful and would see him down the tribunal, he chuckles. He talks a lot of common sense, but he does not listen to anyone and cuts across anything he does not agree with.

The father-of-four likes to exercise his acting muscles by regularly appearing on the stage, but says it can be a dangerous place to be.

I was in one play and three of my daughters were in the audience.

I was on stage but didnt know that behind me a wheelchair was heading my way, he says. They said they found it hard not to shout out Dad and warn me.

But these things can happened when youre preforming live.

Blue/Orange is also a landmark production because it is part of a new partnership between the Ambassador Theatre Group and Theatre Royal Brighton.

It was launched in 2011 under the artistic direction of Spamalot and The Madness Of King George III director Christopher Luscombe with Maria Aitken and Philip Franks as associates.

Each production presented by the company opens at the Theatre Royal Brighton before going on a nationwide tour, followed by a West End transfer. Dandy Dick was their first stage hit with Patricia Hodge.

Were hoping Blue/Orange will be another hit with audiences, says director Christopher.

Its hard to say anything about it without giving too much away, but it will surprise you.

And with that its time to leave Robert, Oliver and Gerard to return to the world of Blue/Orange as the battle of wits continues.

* Blue/Orange opens at the New Alexandra Theatre, Birmingham, on Tuesday for a week-long run. Box office: 0844 871 3011.