As he had been taught, he was the weapon.

He reached into the backpack a final time for the box of matches. He tucked the pistol into his pants and opened the box quickly. The door at the far end opened again, and he knew they were coming to stop him, seeing this moment as their opportunity, or perhaps realizing what would happen next. He fumbled the matchbox in his excitement, the wooden sticks spilling onto the floor. He heard cursing and shouting, but it didn't matter, he had a match in his hand now, and with a stroke it was alive, and he let it fall.

The air around him moved, heated, and he saw flame race over the floor of the car, eating the petrol, taking purchase, growing hotter. The man at his feet made a noise as he caught on fire, and he glanced down to see that his own clothes had also caught, felt the fire climbing his body. He looked down the length of the carriage, saw that the flames now held the others at bay, felt the flames sear his skin as his shirt caught.

From the corner of his eye, he saw the blackness of the tunnel open to the harsh light of the station.

He pulled the gun from his waist, put the barrel in his mouth, and pulled the trigger. • It happened again three minutes later, on the Bakerloo Line, as the train pulled into Piccadilly Circus. • And again, seven minutes after that, on the Northern Line, at King's Cross. • When the final numbers were in, the death toll stood at three hundred and seventy-two. Very few of these fatalities came from direct contact with the terrorists, all three of whom had used essentially the same technique: the gun as the instrument of terror, to empty the car and to buy time; the petrol as the primary mechanism of attack, to set the trains aflame and to force them to stop on the tracks.

As anticipated, the Underground suffered from not one but two weaknesses, and the terrorists had exploited both. The first was that, at any given time on the tube, there were more trains in motion than there were stations to receive them.