I grew up in the country and I've always loved horses, so setting my new Killing Eve novel in the racing world was an easy choice. Few occasions can rival a summer race day at Ascot, Newmarket or Goodwood. There's the glamour and excitement of the event, there are the dizzyingly high stakes, and there are the horses themselves. Beautiful, streamlined creatures bred for speed and top-level competition.

In Killing Eve: Long Shot, we see Eve and Villanelle thrust into this world when a valuable horse is stolen. Its owner, Majid Ismailov, has his sights set on the world's most prestigious race: the Arc de Triomphe, run annually at Longchamp in Paris. The story leads up to this event, and to the heart-stopping running of the race itself, but it also takes us behind the scenes of a top-tier training stable, where an encounter with a million-pound filly, Sofinisba, proves an epiphany for Villanelle.

I needed to make sure that all of this was accurately portrayed, so I went to see an old friend, a lawyer specialising in horseracing issues. He's married to a successful trainer based (like my fictional character Majid Ismailov) in Newmarket, the headquarters of British horse racing. I learnt about the practical business of training and racing horses, but also about the extraordinary economics of the sport. The prizes for classic races like the Derby and the Ascot Gold Cup are impressive - a Derby winner can expect to take home around £900,000 - but it's at stud that a horse earns the real money. The lifetime earnings of the top stallions are in the tens of millions.

So it's a big money game. But for me, as for Villanelle, it's all about the horses themselves. I knew that certain racehorses had presence, but I wasn't prepared for the extraordinary magnetism of some of the animals I met. You'll meet them too, in Killing Eve: Long Shot. You'll see them galloping through the dawn on Newmarket Heath, and racing into the final furlong of the Arc de Triomphe as the novel's deadly last act plays out. Every Killing Eve novel has its world. A framework for its heroines' violent and passionate adventures. Creating this one was a particular joy

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Killing Eve: Long Shot is published on November 1, and available for pre-order now