Cardiff Central - enter through a tunnel with steps to the platforms. Like Birmingham New Street or Amsterdam Centraal, except is Cardiff is older and the steps lead up.

Approaching Bristol Parkway, your eyeline is at the roofline. Ridges into the distance, only broken by the occasional runaway Leylandii. Strong and sudden realisation that where I live is not-like-this. A businessman, bald and silversuited, sits down diagonally opposite. Soon he gets up and strides to the toilet, then back past me to get a sandwich. He eats, I read, we ignore each other. As he tidies his rubbish, he knocks an empty cup onto my bag then to the floor. He apologises, backheeling it under his seat.

He leaves and is replaced by a beautifully brown-eyed woman. Put off by the bald's debris, she sits directly opposite, ignoring conventional train ettiquette. The conductor passes. Any tickets from Swindon? Rummaging, she finds it but he's already gone. We exchange a conspiratorial smile, her face lighting. I glance at the floor, see her pointed black boots. Thinking of Rosa Krebb's knife blades, feel suddenly vulnerable.

She puts on makeup at Reading, shaping her lips with brief accurate strokes. Crossing her legs, grazing my shin, she projects a sharp toe into the gangway. Suddenly she relents and slides into the window seat.

The vacant place is taken by a sad kohl-rimmed girl. Tight headscarf, hoop earrings. Smells of day old chips and week old sweat. Strapping on a walkman, she stares resolutely though the window, lips pursed. Outside it's raining. Looking again, the sky is blue with perfect winter cloud.

We empty in silence, strolling and hurrying through Paddington's vast and vaulted engine shed.