Interviewed to promote next week’s Series 9 DVD release, Firth commented: “It breaks one of the fundamental rules of television drama: you don’t kill your heroes! That’s what people come back to see week after week, but we kill our heroes and through some bizarre sequence of events that’s worked.”

He added: “People manage to fit in very well – we bring in new characters and they’re quickly accepted by the audience. It seems to have been a plus rather than a minus.”

> Buy the Series 9 boxset on Amazon.

Spooks will return for a tenth series this Autumn.

Watch the full interview with Peter Firth…