Broadchurch star David Tennant has said he found the secrecy surrounding the hit drama “exhausting”.
The show, co-starring Olivia Colman, is returning for its final series on Monday on ITV.
Former Doctor Who actor David, 45, told Radio Times magazine that knowing the crime drama was coming to an end felt “like a loss”.
He said of the security surrounding the plot: “Everyone found it rather exhausting. We were all issued with different passwords for different things.
“So new bits of script would come through and you’d forget what your password was and have to phone somebody up and prove it was you.
“That drove me mad, if I’m honest. I’d phone up the office and go, ‘I need it on paper, I can’t cope!’”
None of the actors were given the final script so the storyline could be kept secret.
“There was a recognisable amount of security. Honestly, it was a nightmare,” said David, who returns as DI Alec Hardy.
Olivia, 43, who plays DS Ellie Miller, told the magazine she tried not to cry in the new series – having previously confessed that audiences might have seen her weep in character too often.
“I was really trying not to cry too much, but it was quite hard.
“When the camera was on (co-star) Julie (Hesmondhalgh) and she was doing her scenes, it was so unbearable to watch.
“When the camera was on us for our reaction shots, I had to ask her to do it slightly less well so that I wouldn’t cry.”
She dismissed any idea that she is a national treasure and said she finds it difficult to deal with people trying to take selfies with her when she is out doing normal things.
“If you’re going to a work do and you’re all dressed up for an awards ceremony or something, it’s fine because it’s work,” The Night Manager star said.
“But if I’m going out with my husband and kids, I’m not at work. I grew up without the selfie thing and I find it quite alien and odd.
“I said something the other day to someone who asked for one. I said, ‘Just because there’s not a photo doesn’t mean it didn’t happen’. I think they thought, ‘What a weirdo’.”
She said talk of national treasure status was “flattering, but I feel I haven’t earned that”.
“I don’t know what it means… (Dame) Judi Dench and (Sir) David Attenborough – they’re national treasures. I feel slightly embarrassed that, at the moment, I’m not in their sphere.”
The third series of Broadchurch features a sexual assault storyline.
The show’s creator Chris Chibnall said sexual assault is often “not treated with the time or delicacy it deserves”.
“What I did was to deliberately slow the pace down because I wanted to go into detail of how you report an attack,” he added.
This week’s Radio Times is on sale now.