ow, I know a fair amount about art.

I know that red paint was more valuable to Aztecs than gold and that Sir Isaac Newton invented the colour wheel.

I know that when the Mona Lisa was stolen from the Louvre the empty space attracted more visitors than the painting and when lit a coloured crayon will burn for thirty minutes straight.

I even know that in 1964 a Swedish journalist exhibited pictures drawn by a chimpanzee to see if professional art critics could tell the difference.

(For the record – they couldn’t.)

But it doesn’t matter how many facts I know about art, I don’t totally get it. And I can say that with some confidence, because that’s exactly what my art teacher, Mr Randulph, wrote on my Year Nine Report Card.

All of which means I may have visited every other museum and exhibition in London more times than I can possibly count.

But I have never, ever been here.

The same cannot be said for Jasper.

From the moment we walk through the big glass doors of the National Portrait Gallery, he looks different.

Poised, determined, comfortable.

I stare at him in surprise.

Has he transformed, or is he always like this and he’s just finally in the right environment? The way a wolf in a grey, dull city would just look like a big dog until you finally saw it in a forest: being who it’s meant to be.

Without a word, Jasper carries on walking.

Straight through the high-ceilinged, wood-panelled rooms, past pictures of people I recognise – Shakespeare, David Bowie, Jane Austen – and people I definitely don’t: rosy-cheeked children, men with austere pointy beards, and women with elaborately jewelled dresses and tiny dogs.

Finally he stops in front of a black and white photograph of Winston Churchill.

“There,” he says with a nod. “Your inspiration.”

I look around the room, because I’m obviously missing something.

“Umm.” I glance at Jasper’s profile, but he’s still staring at the picture. How do I put this politely? “I’m not entirely sure you understand the world of fashion modelling, Jasper.”

In all my time as a teenage model, nobody has ever asked me to be like the man who led Britain to victory in the Second World War.

“This was taken in 1941,” Jasper says, ignoring me completely. “Churchill was tired and didn’t want his portrait taken. Yousuf Karsh, the photographer, refused to give him a drink, ripped the cigar out of his mouth and took the photo before he could respond.”

I look at the photo more closely. Churchill looks genuinely furious: belligerent, bullish, as if he’s seconds away from ripping the room apart.

“This photo helped to win the war,” Jasper adds, almost as an afterthought. “It showed how terrifying and inflexible he could be.”

Then Jasper turns and continues walking.

He stops in front of a portrait of a pretty lady in a blue dress.

“This was the wife of the artist’s best friend,” Jasper says. “He was in love with her, and she never actually knew it. This was his way of communicating how he felt.”

Then, without waiting for a response, he turns and keeps walking, pausing in front of a painting of a woman sleeping peacefully with a hand curled under her face.

“This is Lady Venetia. She died an hour before this painting was made. Her husband was so heartbroken he commissioned a painter immediately and kept this next to his bed for the rest of his life. He believed her spirit had gone into the painting.”

A lump rises into my throat. That’s so incredibly sad, and so incredibly beautiful.

And also a bit like a creepy Oscar Wilde novel.

“Jasper …” I say, clearing my throat. “I’m sorry, but I don’t understand.”

“Every picture tells a story, Harriet. Sometimes we know what the story is. We know it’s rage, or sadness, or love, or grief. And sometimes we don’t. But they all have one.”

He gestures around the room.

Blinking, I lean towards a large painting of a young girl. She’s standing next to a brown and white dog, a triumphant smile at the corner of her lips.

And the meaning of what Jasper’s saying is slowly starting to hit me.

It’s not enough for me to just be there.

These portraits capture fleeting moments. They’re emotions immortalised, a transient life made permanent: however personal or public, private or shared.

In a world where everything changes, these are points of time that stand still. A way to hold on to something that can’t last forever.

And the same goes for each of my photos.

The fear and confusion in my face when I was trapped in a glass box full of dolls; the bewilderment as I was covered in octopus ink. The glowing snowflakes photo, taken moments after my hand was held for the first ever time. The second I fell in love, immortalised in a shining lake.

Even those first few clumsy polaroids: the anxiety of a bullied girl, thrown into a world she didn’t think she could or should be part of.

All the stories I’ve already told, without even knowing it.

“Harriet,” Jasper says, turning and looking straight at me, “as a model, you are a blank canvas. It’s up to you to paint a picture.”

I blink at him as the box in my head rattles a few times. That’s just what Nat said too, isn’t it?

I’ve never seen my job as anything more than meaningless expensive photos of clothes before – with me as a giant living breathing doll – but maybe it’s more than that.

Maybe it’s art too.

Huh. I should go get my Year Nine Report Card and ask for a reassessment: I think I finally get it.

I stare at Jasper.

You know, it’s weird. I’ve always thought his face was round, but it isn’t: it’s kind of a heart shape. And though I initially evaluated his hair (a little unkindly) as mousey, up close it’s actually bronzes and browns and golds and blonds.

Lots of bright colours, mixed up together.

“Thank you,” I say after a short pause. “You’re a good friend.”

“Yeah.” Jasper smiles slightly. “Probably too good. I’m expecting my medal any day now.” He hands me my folder. “Come on, Harriet-uccino. You’ve got a big day tomorrow. Let’s get back home.”