K, I officially give up.

The Whistler Sliding Centre in British Columbia is the steepest and fastest bobsleigh track in the world. It starts off at 938 metres high then hits a 152-metre vertical drop, allowing amateurs to hurtle downhill at 125 kilometres per hour.

Headfirst, without any brakes or control or idea how to stop it.

Pretty much exactly like today.

Breathing out, I blink at the London streets.

In less than fifteen minutes, it’s gone from being dusky to night-time and I have a feeling I’m about to be in a lot of trouble. Annabel didn’t even bother leaving voicemail: that’s how little interest she had in shouting at me indirectly.

I hesitate for a few seconds – maybe she’ll get bored and give up redialling – then I realise the sun will explode before that happens and click the green button.

“Umm, hello?”

“Where are you? It’s dark, Harriet. I know you’re sixteen but you can’t just disappear for hours without telling anyone where you’re going.”

“I’m in the … park,” I edit optimistically. “Just enjoying the wonder of nature, flowers and … whatnot.”

I am walking past a patch of semi-dead grass right now. The fact that it’s in our capital city is neither here nor there.

There’s a tree, a pot plant and a pigeon.

It’s a park.

“Right,” Annabel sighs. “Well, we’ve lined up a documentary about stars and we thought you might like to watch it with us.”

“Ooh yay,” I hear Dad say loudly in the background. “Tell my eldest it just wouldn’t be the same without an elaborate running commentary all the way through.”

I sense sarcasm.

In my defence, I do know nearly as much as the official narration.

“We have popcorn,” Annabel adds cunningly. “And chocolate buttons. Also some kind of chilli-mango worm.”

“Salsagheti,” Bunty says cheerfully into the phone. “I bought them in Mexico and there’s a picture of a duck wearing sunglasses on the box so they should be immense fun.”

“When can we expect you?”

“I’m really sorry, Annabel,” I say, glancing at my watch. “I’ve already got plans.”

I turn down the road towards the tube station. London is glowing and lit from within. Every building I walk past has something exciting happening inside it. Friends huddled in restaurants and coffee shops: eating, laughing, talking.

Having fun in their happy little groups.

All I want is to get back to mine.

“This is important too.” There’s the click of a door being closed quietly. “Harriet, you’re coming home right now. I’m not asking you. I’m telling you.”

Oh, what?

Quickly, Harriet. You have an IQ of 143: make up an impressive reason not to. Weighty, unquestionable. Profound in its deep reflection of the human race.

“But I don’t want to,” I hear myself whine. “I want to hang out with my friends.”

“Well,” Annabel says sharply, “sometimes growing up means doing things you don’t want to do, Harriet. I’m sorry that spending a single hour with your family is one of them.”

“That’s not what I—”

“You have fifteen minutes and then I expect to see you walking through the front door. Do I make myself clear?”

And the phone goes dead.