Daniel Mays finds it "surreal" that Queen Elizabeth watched 'Line of Duty'.
The late monarch - who passed away in September aged 96 - is said to have been a fan of the BBC police procedural drama, but it is thought she disliked "mumbling" on the show.
Daniel - who played Sergeant Danny Waldron in 2016's third series of the programme - said: "It's surreal to think that the queen is sitting there watching it."
Author and broadcaster Gyles Brandreth claims in his new royal biography, 'Elizabeth: An Intimate Portrait', that the queen liked watching 'Line of Duty' to "keep her spirits up", but wasn't a fan of the "mumbling" in that and other shows.
But Danny insists his character is innocent when it comes to speaking in a quiet and indistinct way.
He said: "I'm not guilty of mumbling in 'Line of Duty'. My diction is always on point."
The star has gone on to appear in TV shows 'Good Omens' and 'Inside No. 9', and films '1917' and 'Fisherman's Friends', but he is still regularly asked about 'Line of Duty', despite only appearing in the show briefly because his character was killed off.
Speaking on 'Good Morning Britain', Daniel added: "What is extraordinary is 'Line of Duty' was a two-week shoot for me. I was going on to do a play at the National Theatre.
"My character didn't last very long. It was a really intense two-week shoot, and on every talk show I go on now they talk about 'Line of Duty'.
"But I'm not complaining. I'm so proud of that role. It was such an amazing show to be part of."