London-Oxford Street, Marble Arch 07 August 1517 GMT

The planning was exceptional, the result of two years spent preparing for the action, an operation meant to run like clockwork. And much like clockwork, it nearly failed, simply because men are not machines, and they feel fear.

When it came upon him, it came by surprise. It stole his breath and cramped his stomach, and for an instant he was certain he would wet himself. Just inside the Marble Arch tube stop he balked, the wash of passengers flowing past him in both directions. He felt the uncomfortable pressure of the glass bottles in his backpack, felt the sweat springing to his palms. Adrenaline filled him, made the stink rising from the tunnels all the more rank, the perfumes and deodorants and colognes that much more cloying. The noise of the station, the echoes of the trains and the voices and PA, became almost unbearably loud, adding to the sudden rush of vertigo.

For a second time, he thought he might vomit.

He steadied himself against the wall, closed his eyes, fought to control his breathing. Of all the things he had practiced, of all the things he had envisioned the eleven times he had made this same trip as a dry run, he had never considered this. He had known he would be nervous. He had even acknowledged that he might be scared. But this level of fear was unexpected, and it unmanned him.

Worse, it made him question his faith, and that added a new emotion, a rising sense of shame. He willed himself to walk on, to continue through the turnstiles and onto the escalator and down to the platform, painfully aware that seconds were passing, that the schedule they had so carefully crafted was now in dire jeopardy. And still he couldn't move.