Euston is an odd station, not least for the distance between the platform "entrances", where screens parade the travel updates, and the actual platforms. Arriving at platform 1, Andrea insisted we escape the crowds and proceed down to the platform. I capitulated: yet another mistake. 

Down the long concrete slope we trooped and out onto the eerily empty platform. Alone now, with time to kill, I asked Andrea a little about her life. Between swigs of Coke she spoke about living alone, of a life on benefits, of estrangement from her parents — the embodiment of a broken Britain whose reality the liberal Left denies so stridently or dismisses as "pessimistic". Tears shone around her eyes as she told me of the abortion her mother had tricked her into having. 

As I listened to this I was also becoming increasingly aware that 7 o'clock had rolled round, and 7.10 and 7.15 and still no train. 

This one felt like a real fix: Andrea didn't want to move, but the platform was empty. I had to check the screen. But I had also to give her a sign that I wasn't going to run off. 

"Listen. The train's not here. I'll check the boards. You keep an eye on my bag."

My biggest mistake yet.

Now I'm running around the concourse like a headless chicken. It's 7.20 and the train has changed to platform 12. 

I raced back to platform 1. And of course: 

She was gone, with my bag, containing most of my life in written form.

I'm panicking, darting in and out of people trying to spot her, trying to remember what she looked liked like. 

Three transport police gazing up at the boards. I dived into my story, realising as I voiced it how ridiculous it sounded.

"You left your bag with a stranger?"