Line of Duty's H star on season six finale and keeping it a secret: 'I've been sitting on it for a long time'

The answer was a surprise to many viewers, but the actor who ultimately played the elusive "Fourth Man" has stated that "looking back it all makes sense".

DSU Ian Buckells (played by Nigel Boyle) was at last unmasked as the corrupt cop who has eluded AC-12 for so long. (If only Buckells could learn to spell “definately” correctly...)

On finding out that he was the fourth man, Boyle said in a statement that showrunner Jed Mercurio had pulled him aside for a private chat when filming for season six resumed.

“We’d had the first four scripts and started filming some of Series 6 when we had to stop due to the first lockdown. When we were about to resume filming, Jed sent me a text saying, “Are you free for a chat at some point today? Don’t worry it’s not that call…”. Which I took to mean that I wasn’t going to end up dead! But I was still quite nervous and not sure what he wanted to talk to me about. He called me and said, “the scripts for the next episodes are going to be sent out imminently and so it’s time to tell you the secret that I’ve been keeping, you’re going to be revealed as someone rather significant...”"

Boyle said he was "buzzing with excitement," but that prior to his conversation with Mercurio, he'd never suspected his character.

“I was buzzing with excitement! I never suspected it because I know how Jed leads people down the garden path with really good red herrings, so I didn’t really pay too much attention to things like Buckells’ golf clubs etc, but clearly I should have done! I’d fully bought into the idea that Buckells was low on competence levels but looking back it all makes sense!"

However, he worked hard to keep the secret, well, a secret.

“I’ve been sitting on it for a long time! The only person I told was my wife, nobody else, I know how much is at stake! Even if you tell someone you trust with your life, they might tell someone they trust with their life and then suddenly more and more people know! When friends have asked me who H is I’ve just said there isn’t an H," he added.

Line of Duty is well known for its cat-and-mouse interrogation scenes, and Boyle was understandably "nervous" to film his own.

“It was amazing to read the scripts and see the interrogation scenes. It had always been on my bucket list to do them and to find out I had two of them was great!

"I was quite nervous about filming them, as anyone would be as it’s all done in one take, but I just did what I always do and made sure I was super prepared. Martin, Adrian and Vicky have done them so many times and were so supportive and brilliant to act opposite, they were full of encouragement. We were isolating so had lots of time to prepare together. It was tiring, shooting whole scenes over and over again, but I just relished it," he said.

• For the latest news and expert tips on getting the best deals this year, take a look at our Black Friday 2021 and Cyber Monday 2021 guides.

"It’s a joy to be part of the show in the first place but to have your character getting these sorts of scenes is something pretty special.”

Line of Duty Series 1-6 is available on BBC iPlayer now, and we have all the latest news on Line of Duty season 7. Check out the rest of our Drama coverage, or take a look at our TV guide to find out what else is on.