In the corner of Hyde Park, set back slightly from the road and the soap boxes of Speakers' Corner is a small flight of descending stairs. It's an unassuming scar on an otherwise barely blemished field.
Tiny and unnoticeable, it's locked to the public. Behind the door, a concrete access tunnel winds a quarter mile beneath the park and the five-lane monster of a roundabout that is Marble Arch.
It was through this door that Nike led us.
Strange, really. We were in Hyde Park to run a timed-mile. There's plenty of space - they could have picked any inch of grass to run on - so why did we have to go underground first? Presumably to get changed...
How wrong we were. Along the tunnel lies a car park filled with luxury cars and a electrified fence to keep them safe. Glowing orange, pink, and purple, the tunnel and the car park were lit a night club. Giant speakers, giant screens, Paula Radcliffe, and Steve Cram.
Yep, this was more like it. A true Nike event. They weren't going to organise a simple jog around the park now, were they.
We were givens some kit, naturally. We were shown a video, of course. We were coached as to how to warm up and prepare psychologically, thanks for that. We stretched. We jogged. We challenged our co-ordination - or mine at least - with dynamic exercises.
By the starting line, I felt slightly confused, slightly muddled, but almost prepared for what was to come.
Five beeps. Go on the fifth ... ... ... ... ...
And we were away. Streaking along (I'd like to think) between the rows of Bentleys, Mercedes, and BMWs, twisting around the pillars of the car park, following the yellow and blue markers with our eyes, and spinning our neon trainers furiously.
I lost my running partner pretty quickly. I overtook one, I overtook two, I overtook three or four.
And then I was alone. The car park was empty. All I could hear were the far away cries of the finish and my own breath pounding out a mistimed rhythm.
One lap. Two laps. The corners were tough. Turning was tight and on each straight I settled into a comfortable pace, before having to flex my knees and adjust my balance again.
Finally, lungs burning, it was the final straight. I lifted my arms and feet as high as I could and went for a 'sprint' finish.
The final straight had a twist in it's tale - a long slow corner back up the access ramp we'd started down.
I hadn't factored that in at all. Slowing down, I was overtaken by my running partner. Damn. A slight kick in the teeth, but a time of 5.58 I was very very happy with.
A bottle of water and a bag of popcorn later, and we were outside once again. Back to the park, back to the tube, ready for the commute home.
I'm slightly hooked, I have to say. I've been focusing on distance for the past year, but the mile might be my new best friend. I'd love to go back again next year and try it out once more. Hopefully I'll improve.
Keep an eye on Nike UK for more info on #NikeMilers.