n some Micronesian cultures, they believe that sweat is a warrior’s essence.

I won’t go into unnecessary details.

Suffice to say, by the time I reach the address Wilbur texted me, in the middle of Soho, I’ve jogged so enthusiastically there’s Extract of Harriet pouring down the middle of my forehead.

And my back, my knees … the soles of my feet.

I’m basically in the final death throes of the Wicked Witch of the West, and I’m melting all over the reception desk.

Quickly, I wipe it off with my jumper sleeve and try my best to inhale without sounding like a broken vacuum cleaner.

Then I ping the bell and glance around the empty atrium.

This building is utterly enormous.

The furniture’s white leather, the walls are entirely exposed grey brick, and there’s glass, green plants and gravel everywhere, like some kind of giant terrarium made for humans.

“Hello?” I call out urgently, dinging the little bell again. My voice bounces around the room like a ball. “Is anybody there?”

The only sound is another bead of sweat dripping on to the glass desk with a tiny plip.

Oh my God: I must have missed the casting.

Who are we even kidding? The fastest mile ever run by a woman is four minutes, twelve seconds, and I don’t think I’m in danger of beating that record any time soon.

At one point of my journey I ended up air-vomiting against a lamp-post.

I scan the room again: still nothing.

Then I spot a paper sign stuck on a door, with this written on it in black marker:

Heart still hammering, I rip my bulky coat off. I unwind my long, sticky red scarf, throw it over my shoulder and rearrange my sweaty T-shirt.

Then I start trotting down the corridor.

It feels like it goes on for miles – like one of my horrible cross-country nightmares – but with a final burst of exertion I finally reach a door with CASTINGS written on it.

Panting, I stop with a wave of relief.

And also a wave of nausea: I’m really not built for this much physical activity.

“I’m here!” I breathe, rapping sharply on the door and wiping several drips from my forehead. Please. Please don’t have gone already. “Don’t worry, I’m here!”

“Now just hang on a—” somebody says.

But it’s too late: there’s nowhere to hang on to.

With a final wobble my exhausted legs give way: throwing my entire weight against the door.

It opens with a click.

And – with a tiny squeak of horror – I fall face down into the world of fashion.