Line of Duty star Craig Parkinson reveals how he re-filmed Dot Cottan's dying declaration

Was the Morse Code message there in Dot's dying declaration all along? And, how far ahead did showrunner Jed Mercurio plant the seeds of his big twist?

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As fans will recall, Dot gave his dying declaration to DS Kate Fleming (Vicky McClure) after being fatally shot in series three (2016). In series four (2017), it emerged that the incident had also been caught on film by an armed police officer's body-cam – and we got a look at that police footage for the first time.

But in the series five finale, Steve showed us a section of that "dying declaration" video which had never been broadcast before. As Dot was receiving emergency medical attention, his left fingers were seen tapping against his palm.

So, did Parkinson have to go back to Belfast and re-shoot the scene for series five?

"No, I didn't go back and film it," he tells RadioTimes.com. "Because what I did is, I went back to re-film it in series four, so then they had stuff that they could use for series five."

He adds: "Very early on in series four, they just said, 'Oh, can you just pop over to Belfast and just do this adding-on of the dying declaration.' And luckily I could.

"But I'd do anything for Jed, he's absolutely incredible and he has changed my career, really, you know."

Cryptically, Parkinson seems to have forgotten whether he was asked to send that Morse Code message while filming the extra footage for series four and five, or whether the latest addition was digital trickery.

Had Mercurio asked him to tap his fingers during the reshoot? "From what I remember, yeah," says Parkinson, before adding: "Or that might have just been somebody else."

The continuing saga of the dying declaration has given the character – known as "The Caddy" – an impact long after his death. "Even though Dot very sadly left us at the end of season three, the shadow of Dot has been around in every series so far and maybe he'll pop up again in six. Who knows!" teases Parkinson.

He's not the only one who likes to tease. Back when series five was in production, Mercurio stoked rumours of Dot Cottan's return during filming, sharing a photograph of Stephen Graham on set in Belfast along with a heavily-bearded Parkinson. "The Caddy's back from the dead to plot more mayhem," he tweeted.

According to Parkinson, this is classic Mercurio – and in fact, the Line of Duty creator got the two men to pose for the photo with the sole purpose of "winding up" his fans.

"Well, I was just – I was in Belfast for half term, with my little boy, and they were there, and Jed said, 'Oh, come and say hello with everybody,'" Parkinson recalls. "So I went down to set, and I hadn't seen Stephen for ages, and I saw Vicky and Aidy [Adrian Dunbar], and Maya [Sondhi], and Jed said, 'Oh, can I just do something? Can I just take a photo of you and Stephen?'

"I said, 'What are you up to?' He said, 'You know what I'm like!'

"So, he's a big winder-upper, he seriously is. He loves a wind-up. He really stokes the Line of Duty fire, and he gets off on that."

While Mercurio's tweet (and his habit of pulling off BIG twists) left us actually wondering if Dot was somehow still alive, Parkinson insists his character is 100%, categorically dead. "No, I think it's safe to say, Dot is in the sky," he says, adding after a pause: "Or maybe he's in hell. Who knows."

But has Mercurio given any hint as to whether the character will play a posthumous part in the plot of series six?

"I have no – I have been given – no indication whatsoever," says Parkinson, choosing his words carefully. "And even if I did, I have a blood oath with Jed Mercurio – I couldn't say anything." In case all this talk about blood oaths gets us too excited, he quickly adds: "But 'no' is the answer."

Whether he'll ever appear in the show again or not, a string of recent jobs have reunited Parkinson with his Line of Duty co-stars. Upcoming Sky drama Temple sees him appear with one of his "best pals" Daniel Mays (aka series three's Sergeant Danny Waldron), while new ITV crime drama Wild Bill was a chance to film with "good mate" Tony Pitts (aka bent copper DCS Lester Hargreaves).

And then there's Year of the Rabbit, a brilliant (but bizarre) Victorian police spoof in which Parkinson has a guest role. The six-part Channel 4 comedy also features Matt Berry, Freddie Fox, Susan Wokoma, Alun Armstrong, Sally Phillips, and – intriguingly for Line of Duty fans – Keeley Hawes.

Hawes, who played DI Lindsay Denton in the BBC drama, has been cast as the "mysterious" Lydia, while Parkinson gets a key cameo in one episode.

The Line of Duty co-stars never meet on screen, but – without saying too much – there is an unlikely connection between their characters. "I'm sure people will pick up on that," Parkinson says with a laugh.

Parkinson makes his appearance in Year of the Rabbit when Matt Berry's character, a hard-drinking policeman called Inspector Rabbit, comes across a hostage situation at an East End factory.

A man (Parkinson) is threatening to gas a roomful of girls and has his thumb on the trigger-switch; it's up to Inspector Rabbit to talk him down. The timing is inconvenient because Rabbit has another place he really has to be.

"It was really fun to film, because it was quite intense and the stakes were super high for my character and for Rabbit at the same time," Parkinson says. "So, we're both playing two different levels of anxiety, really. And then obviously when we cut we could just have a laugh."

The Channel 4 comedy was also a chance to work with screenwriters Kevin Cecil and Andy Riley for the first time since 2004. Back then, Parkinson was in the very early days of his acting career when he bagged the role of Martin the Tout in an episode of Black Books.

"One of my first jobs was an episode of Black Books that Andy and Kevin wrote with Dylan Moran," he says. "And since then my career has gone down quite a dramatic route, but my first love is comedy – so I've been slowly over the last 15 years trying to get back to doing comedy, which is really hard.

"And also, when I read what Matt was doing and what Andy and Kevin were doing with Rabbit, I was going, 'Well, I haven't seen anything like that on telly before.' It's something like the Sweeney, but set in Victorian London.

"I just think that it whips along at a cracking pace, and it's a joy.

"I don't think people will have seen anything like it."

Year of the Rabbit begins on Monday 10th June at 10pm on Channel 4