He was a beautiful horse – deep chestnut with a flaxen mane and a thick honey-blond tail that flowed almost to the ground. There was one perfect white sock on his near hind leg and his haunches were muscled, but his limbs were delicate and his neck set perfectly into his elegant shoulders. As he reared up on his hind legs, he turned to look at me. His dark liquid-brown eye had such a soulful expression that it seemed impossible that he wasn’t a real horse. To think that an artist had created all of this with his hands!

“I want to take him home,” I told Dad, laughing.

“We can’t,” my dad said. “He belongs here, and besides – that painting’s worth thirteen million pounds.”

I was heartbroken until we went to the gift shop and Dad bought me a box of paints and a postcard of the painting.

“You can make your own horse now,” he said.

That afternoon, I tried to paint my own Whistlejacket. I struggled hard to get the proportions right – to recreate his broad neck and the dip of his back and the curve of his rump. The legs were tricky! Especially his hooves. I found my new paints were a blunt instrument, too drippy and squishy, and so I swapped to a plain HB pencil. Using the pencil wasn’t as colourful or fun, but I wasn’t interested in painting like a little kid. I wanted to make my horse perfect, and with a pencil I could refine my picture, reworking the lines, rubbing out the bad patches and redoing them until I was satisfied.

I did lots of drawings of Whistlejacket, and each time I was finished I would show them to Dad and he’d put them on the fridge. At first they were pretty clumsy, but I got better fast. I mean, I was only five and most five-year-olds do drawings that just look like scribbles – but pretty soon I could do ones that really looked like a horse. I remember I did one that was really good, and it almost looked like him. My dad looked at it for a long time in admiration and then he said. “Maisie, you’re a prodigy.”

“What’s a prodigy?” I asked.

“Someone who is very, very good at something at a very young age. Like Mozart.”

“Did he draw horses then?”

“No. He played the piano.”

“What’s the point of being good at that?”

“Different people are good at different stuff,” Dad said.

I decided at that moment that I would only ever be good at drawing horses.

The next weekend, we caught the bus to Hyde Park. Dad had bought me a new sketch pad with thick, white textured pages, and he’d made us lunch to take with us.

“There are horses here,” Dad explained. “They keep them in stables not far away, and they’re allowed to ride them through the park.”