I went to the London premiere and took my young daughter along. During my hermit sequence, when my thousand-year-old face rapidly gets younger and then ages again, a little voice piped up, ‘That’s not my daddy!’ Fortunately, I was sitting next to her, so I could explain that it was just make-up.

I said to Joe Massot, the original director, I want a full moon and I want snow. We agreed that snow might be difficult to organise, so we decided just to aim for the full moon. As it happened, when we arrived in Scotland and set up, there was still some snow on the ground, although it did melt during filming. And it was still ridiculously cold. I had to go up and down that rock face a few times, and I really felt it. On the first ascent I thought I’d got it right, but they kept saying, OK, let’s do it again. Each time, I could feel myself getting more reckless and frozen.