Jed Mercurio has admitted it is "never far" from his thoughts to kill off one of Line of Duty's "golden trio".
While many of the guest stars on the popular police procedural drama have met their maker, AC-12's Ted Hastings (Adrian Dunbar), Kate Fleming (Vicky McClure), and Steve Arnott (Martin Compston) have been constants throughout the series, but Jed has insisted "nobody is safe" in the upcoming sixth season.
He said: "It's never far from my thoughts, honestly.
"I think we all get on brilliantly, but everyone knows that we're serving something bigger than ourselves, which is 'Line of Duty'.
"One of the things about the show is that nobody is safe.
"That is what keeps the audience on the edge of their seat.
"So I know that it would be a sad day, but all the main cast realise that it's possible.
"You know, we're mates, we talk about it, we joke about it. It's something that no one would relish, but everybody would understand."
This year's sixth series is seven episodes for the first-time ever, as opposed to the usual six - following the first season's five eps - and Jed admitted the enforced seven-month delay in filming, due to the coronavirus pandemic, played a part in extending the series.
Speaking to BANG Showbiz and other media in a webinar ahead of the new series, he added: "It would've ended early if we'd done six, because we had more stuff.
"It wasn't the case of planning seven, it was just the effect of the interruption of shooting and when we went back we ended up, for long periods, working with two units, for all kinds of reasons relating to safety.
"Getting through the shoot faster, being able to have crew who could step in if departments had to self-isolate, so that meant we were able to shoot more additional material than we normally do.
"What we found when we got to the end was we initially conceived having a 90-minute episode six.
"But with all the additions it was pretty clear it was going to be two hours.
"Everybody agreed it was best to split the last episode into two, and that created episode seven."
'Line of Duty' series six begins on BBC One on Sunday (21.03.21) at 9pm.
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