The John Lewis Christmas advert is a beloved British tradition. What was your reaction when you were first approached to star in it, and how does it feel to join such a cultural phenomenon?

I was amazed! Surprised, amazed and utterly flattered and thrilled.

How did you find the experience of shooting the advert?

It was such fun to film - so much more than I actually thought. It was completely brilliant. I loved working with our director Lucy (Forbes), she was great fun. The whole thing was fantastic and I loved every minute of it. We shot it in the middle of the summer and there I was pretending it was Christmas, but that's what I like doing. Pretending things are real when they aren’t.

Your career is so varied, from spy stories to live theatre – how did it feel to put on a different hat to play this role?

I just turn up willing to do whatever they want me to do and with enthusiasm. I’d spoken to Lucy about the story and read the script and agreed to that. So there wasn’t much acting required to be honest because it was all so fun and likeable. I really enjoyed it much more than I thought I would. We shot in this amazing studio space with a reconstructed London, which I thought was absolutely thrilling. I loved it. Although the tuktuk is so not my thing. I mean there was no acting required for that - I can’t stand those things - it grates against every nerve in my body. However, for the greater good I jumped in and let myself go!

Have you had a favourite role during your career?

Not really because there are ones I fell in love with and really enjoyed doing and others that I loved less which have been more successful. The thing to remember when you’re playing a role is that at the end of the day, a film it doesn’t belong to you, it belongs to the director. So you give the director raw material to make what he or she wants - more and more women these days thank goodness - and you give them the wherewithal to tell their story. Now that I have gone to the other side of the camera and have shot my own film with incredibly brilliant actors, I see how thrilling it is to be able to direct actors who really know what they're doing and have amazing experience and an incredible amount of generosity. That is also a secret to the whole thing is you just have to be generous, open and willing to be brave and try out things you hadn’t thought of. And then accept sometimes it’s more difficult, sometimes they don’t want what you suggest, they want something else, and sometimes that’s quite difficult to give up, you have to give up your own kind of pride, and just do what they want. And sometimes that brings amazing surprises and you think ‘oh my god yes, I was so wrong on that one - or I was right.’

So in a film if the performance belongs to the director, would you say a theatre performance belongs to the actor? Or to the audience?

Yes it really does belong to you. I'm currently doing it every night on stage in The Cherry Orchard. So that’s a little surreal, to be in the John Lewis Christmas advert and performing on the West End at the same time. In the theatre you create these characters and you build them for a long time in rehearsals, and then as the play develops it becomes richer and richer. Working with the other actors is like a piece of clockwork - you really have to make sure that you’re all working together and helping each other. To make sure that what you are doing isn’t interrupting their flow - it’s very much a collaborative effort. Especially with this particular production because there are 12 of us on stage and the absolutely miraculous thing is that it’s exactly the same length every evening. We never go one minute shorter, or one minute longer, it’s exactly the same amount of minutes. It’s incredible, it’s never happened to me before. Every time! Right on the dot - it’s very satisfying!

Interacting with other actors is one thing, but how did you find acting alongside your wooden co-star Pickles?

Oh I loved it! I really liked and enjoyed that element. This is a plea - I’d love to be able to do more animation - I love voices and conversations with inanimate objects. It really makes your imagination work and is just a lot of fun. It’s proper playing, like you’re a kid.