Interviewed to promote next week’s Series 9 DVD release, Firth commented: “We start very soon and that will air in the Autumn of this year, probably early October, and I can tell you… virtually nothing! It’s always been the case that the producers have kept their cards very close to their chest, so they’re not really including me as yet in what the storyline’s going to be.”

He continued: “The show’s improved year on year, I think, culminating in last year which is widely perceived as the best year series that we’ve done. So the bar’s quite high, but we can jump.”

Asked about possible plots for Series 10, Firth joked: “We’ve run out of storylines, that’s the truth! We’ve covered every radical group in the world virtually.”

He added: “We have a gifted and talented team of writers who have the ability to look at what might happen and then narrow that down to what will probably happen and then dramatise that. Frequently over the years we’ve been spot on with that and that’s given us some kind of kudos that most programmes don’t have.”

> Buy the Series 9 boxset on Amazon.

Watch the full interview with Peter Firth…