Stella Gonet played the Queen on the big screen in Pablo Larraín’s Spencer, a drama set over Christmas in Sandringham in 1991, starring Kristen Stewart as Diana. Gonet reveals how she channelled the monarch for the role – and what other people’s reactions taught her about the real woman.

As soon as I’d come out of makeup with the wig on, people changed totally towards me. It was extraordinary. “Can I get you anything? Can I do anything for you? Are you all right?” Normally people are very tactile with me but they’d suddenly move out of my way. There was just immediate respect. It was as if I was on a little horse that meant they couldn’t get too close.

The German chap who owned the Rolls-Royce we were using was a passionate royalist and so thrilled. He couldn’t believe it when he met me. He just thought I was the Queen. I thought: “This is just insane. I can’t turn round in broad Scots and say: ‘Don’t be silly! I’m just pretending.’ People seemed to really love and respect her.

I found the opposite with Margaret Thatcher, who I played for ages on stage in Handbagged, Moira Buffini’s play, with Marion Bailey as the Queen. She was just so divisive. Even my sister said: how could you play her?

Thatcher was totally devoted to the Queen. She’d do this incredible curtsey; almost prostrate herself in front of her. I think she desperately wanted to know the Queen, but they were poles apart. She wanted the same handbags, and the longer Thatcher’s reign went on, the higher her hair would get.

The Queen always seemed much more fun than Thatcher, and in preparing for Spencer I thought: yes, she really did have a sense of humour, which we didn’t see very often. She was quite funny, whereas Thatcher just never got a joke.

I think the Queen’s longevity was partly down to having other interests, in particular that huge passion for dogs, horses and the outdoors – as well as those very strong intimacies with her mother and sister and Prince Philip. The arts: not so much. Not a great deal of poetry in there. I don’t think she ever really wanted to go to the theatre.

She was practical. In Spencer, it’s always freezing at Sandringham. I’m sure that’s right; the one-bar electric fire. The film also shows how devoted to her father she was, keeping up George VI’s tradition of weighing guests when they’d arrive for Christmas, and again when they’d leave.

I found it difficult to get her voice, because she was so posh, and her walk was also hard. She carried herself incredibly well, even at the end. She had very good gait. I think it was all that horse riding. You’d see her meeting all these extraordinary people and – nothing. Then you see her at the Derby, charging down to watch!

I also noticed that she’d always ensure her hat was always very far up her head, so her face wasn’t covered. She felt people needed to see her. I think she had huge loyalty to her duty and her people. She took her job at a very early age and did it incredibly devotedly. I think it’s going to be very empty now. I can’t see the monarchy carrying on. But then I’m Scottish, so I can’t really talk about being a royalist.

Gonet and Marion Bailey in Handbagged.

The only brief moment I had to compare with that experience of the temperature changing was in the early 1990s, when I was in a Sunday night series called The House of Elliot. I didn’t really talk to anyone about it when we were shooting; I considered myself a theatre actor and in those days you weren’t sure whether one should do telly, which I know now seems ridiculous. I was hanging out the washing one Monday morning and my next door neighbour said: “Oh my goodness! You shouldn’t be doing that.”

I had suddenly become a different person because I’d been in that little box in their living room the night before. I remember thinking: that’s weird, how bizarre. How many performances I’d done on stage – nothing, ever. People might ask you to sign a programme but, suddenly, I shouldn’t be hanging out the washing.

I think a whole life of that must be very difficult. To live totally for others. To always be on show. Can you imagine? Horrible. I might not be a royalist but I was a huge fan of the Queen. It was an honour to play her.