David Robb has enjoyed a long career. His many TV roles include I, Claudius, The Flame Trees of Thika and Monarch of the Glen, alongside roles in films Young Victoria and Elizabeth – The Golden Age. To audiences today, though, he's the quietly charming Dr Clarkson in Downton Abbey.
He's the first to admit that his role in The Haunting is a bit of a departure for him.
Adapted by Plymouth playwright Hugh Janes from ghost stories by Charles Dickens, the play is set in a crumbling mansion on a desolate moorland. A young book dealer, David Filde, is employed by a former associate of his uncle to catalogue an impressive library and finds an incredible array of rare and antiquated books. As a series of strange and unexplained events conspire to keep him from his work, he realises that if he is to convince his sceptical employer that the mysterious phenomena he is experiencing are real, they must discover the source of the ghostly night-time visitations.
"It's an intense piece," admits David in a break from rehearsals. "It's very atmospheric. It's from a collection of two or three ghost stories put together and it's quite creepy.
"I have played some fairly creepy guys in my time, but I haven't played anybody quite as withdrawn as this guy is.
"There's a history of these kind of plays working well – like The Woman in Black. Audiences like to be kind of scared, in an invigorating way, but they don't want to be scared out of their skins. Hugh Wooldridge, the director, has been filling us in about the audience reaction. They can be quite responsive – there are gasps and the occasional laugh. I think when it works, it's a unique experience. It has to be tremendous."
The Haunting also stars James Roache, recently seen in Coronation Street as the grandson of Ken Barlow, played by James' real-life father William Roache. This is James' first stage role.
"We didn't know each other before," says David, "but he is acquitting himself very well in rehearsal and he does come from acting stock."
David, 64, has been leaving rehearsals every day to complete filming on Downton Abbey's Christmas special, written by Julian Fellowes.
"It's a nice problem for an actor to have and Downton Abbey is delightful to be part of. I'm getting used to being in a global phenomenon... and long may it continue.
"Julian was asked what he attributed the success to. He said that writing hit TV shows was down to timing and luck and things you have no control over.
"He cast 20-odd leading characters and had the first choice on every single person. And he has a very good relationship with Maggie Smith and delivered her to the show. He writes specifically for Maggie and she steals every scene."
Don't expect David to share any secrets though.
"We only get scripts in batches of two, so you race through to see who's been killed or married.
"There are real cliffhangers where no one knows what happens next and there are some real shocks to come in the third series."
He may have made a success of it, but acting wasn't David Robb's originally career choice. "I was destined for Sandhurst and the Scots Guards," he says. "It's interesting that many professionals have a certain degree of performance, like the law and the Armed Forces... especially the Household Regiment! In acting I get to play all of those roles, and I don't get shot at."