Sinead Keenan, who played Addams in David Tennant's final outing, has revealed that she left her scripts in a pub shortly after reading them.
"We had to return the scripts to the production office once we'd finished with them," she said.
"After I'd got the part and I'd read through the scripts, I was with my boyfriend at the time and we were having lunch in a pub, and I left them on the seat!
"He went, 'Sinead - where are your scripts?!' and so we went back and got them and luckily it was fine. It was all very confidential and hush-hush."
Recalling the secrecy around the Christmas specials, she added: "It was one of those things that you couldn't tell anyone. Besides, when you get your scripts, every one was watermarked with your name and the date in case it got out.
"And we were never given a full script. It was unbelievable!"
Keenan currently stars in BBC Three's Being Human.