One of Flora’s rules for life is: Don’t go to Svalbard in winter. Her visit to the Arctic is in May, when it’s light absolutely all the time, and although there is snow on the ground it is not breathtakingly cold. When I visited to research the book it was fine to wander around in jeans and a coat (except when I went out on a boat and got so cold the crew gave me a lovely warm snowsuit to wear). Every now and then it would snow, which was magical: I think, now that I live in a place in which it pretty much rains all winter, I will always have the ‘IT’S SNOWING!!’ levels of excitement when those flakes start drifting from the sky.

However, when I was writing the book I started thinking about what it would actually be like in winter. I wanted to go and look at it because I couldn’t imagine the polar night. The sun is below the horizon in Svalbard from October 28th to February 14th. It felt easier to imagine the white nights than the dark days. Somehow Craig and I ended up booking a trip there. We booked it months ago, and last week we went.

The first thing I discovered was that it’s only completely dark if the sky is filled with clouds. Otherwise it’s blue. Everything is tinged an otherworldly blue colour. The next thing is that it is very cold indeed. When we were there the temperature ranged between minus 20 degrees celsius and a comparatively balmy minus 15. You have to take a lot of clothes with you, and you wear them all. The feeling of that cold air on your face is like nothing I’ve ever experienced before. Indoors is warm, wherever you go, and outdoors is extraordinarily cold, so you end up peeling layers off all the time and piling them up next to you in the bar.

It was a clear day when we went out on snowmobiles, into the blue. The sky was a strange muted blue, and the snow reflected it. The landscape is immense and people are insignificant, which was comforting.

And then there is the Aurora, the Northern Lights. We signed up to a text service run by the man who drives the airport bus: he sends out texts when there’s likely to be an Aurora, and then picks up anyone who replies from their hotels and drives them out of town to look for it. So we ended up riding the airport bus around hairpin bends and up an extremely steep hill, in the dark, hoping for a display in the sky. On the top of the hill (which felt like a mountain but probably wasn’t, comparatively), we stood around in minus 20 degrees for two hours, waiting. There were two satellite receivers up there too, which made it feel very sci-fi. The smudges around the edges of the sky jumped around a bit and there were more stars than I had ever seen before. We got cold. After a while everyone got back on the bus to warm up, and then we got out again, several times. Just as we were giving up, it all happened: the sky was alive with pale green. It danced around, like shifting shapes, moving across all we could see of the universe. The sky was doing things that the sky never does. It was ethereal, otherworldly, and it moved and shimmered. It was one of those things you never forget.

Here are some photographs. Flora should not go to Svalbard in winter – it would be catastrophic for her. But I’m glad I did.