11/03/2014 AT 06:15 AM EST
“I used to live in a house with four guys, all of my friends,” the actor, 33, told PEOPLE Thursday while attending the BAFTA Los Angeles Jaguar Britannia Awards.
“I had to be very careful where the scripts were left, because suddenly you’d come in and someone would [say], ‘I couldn’t help but see that episode four was there.’ I was like, ‘Oh, my God!’ So I tend not to tell anyone. Not even family. No one gets it out of me, which is good!”
That said, Leech did have a few teasers for the next season of the hit PBS show, which premieres Jan. 5.
“There are a couple of things coming up in the series that I’m bracing for, for my character alone,” he said.
“Downton is again in a period of change. The first socialist government comes in, and you have a very conservative house very worried about it. And there are great story lines for characters like Edith, and where she was left at the end of the last [season]. Is she going to be able to deal with the fact that her child is basically no longer hers? Some really, really great stuff.”
As for life outside the grand manor, Leech will appear in November opposite Benedict Cumberbatch and Keira Knightley in The Imitation Game, a movie about the life of Alan Turing, the man credited with cracking the German secret code during World War II.
It was a challenge acting-wise, admits Leech, who plays an intelligence officer. But he credits his time at Downton for mustering up the courage.
“I’ve been lucky enough to have the opportunity of baptism by fire with Maggie Smith over the years,” the Dublin-born actor quips. “It gives you a certain amount of confidence if you can come up to Dame Maggie’s standards, then you’re in a good place.”
• Reporting by SCOTT HUVER