The actor, who plays DI Steve Arnott on the BBC’s hit police show, has said that the “story of natural history we’ve been through for the last six years” is coming to an end and the cast won’t return ” for the sake of it ”.
Speaking below Jonathan Ross’s show, Martin said the future of the show is in the hands of creator and writer Jed Mercury.
“That’s no different for us,” he said. “Jed always takes months later … there are things above our pay, statistics, numbers and all that comes in.
“It simply came to our notice then. But I think it’s important to say, I think this natural arc of history that we’ve been through for the last six years (it’s over).
“It simply came to our notice then. That’s for sure. “
He added: “We’ll come back if there’s a story to tell. But also, if it ends well, sometimes it’s better to leave it. But we really don’t know.”
A trailer for the end of Sunday’s series has promised viewers that the identity of the “fourth man”, also known as “H”, will be revealed.
AC-12 Chief Superintendent Ted Hastings is among the suspects, along with DCS Patricia Carmichael, Chief Agent Philip Osborne, DI Kate Fleming and former Officer Marcus Thurwell.
The Internet is already flooded with theories before the end, as many fans believe Marcus Thurwell is alive, after the character was found dead in his Spanish village – and some then claim to have the proof.
Suspicions have also been raised about DCS Carmichael, as some viewers saw what they believed may be a track that confirms it is “H”.
The series has been a huge success for the BBC, with the penultimate episode averaging 11 million viewers on nightly ratings.
Some 15.2 million have also watched the first episode, according to consolidated figures that take into account viewers who watched the recovery services and other devices during the 28 days since it aired.
Jonathan Ross ’show airs on Saturday at 9.35pm on ITV, while Line Of Duty ends on Sunday at 9pm on BBC One.