“I’m sure I don’t need to tell you,” Lockhart began, “that these canisters need to be handled with great care. Ignore the noise around you, ignore the gunfire, ignore the alarm. We’ve only failed when we’ve been killed. Understood?”

Leni and Pugh nodded.

“Pugh, I want you to take the canisters off the rack and pass them to Leni. Leni, you will then pass them to me. I shall pack the still. When we’ve got halfway, I shall place the explosive with a ten-minute fuse. That will give us enough time to pack the remaining canisters and seal the lid.”

“One question,” said Leni.

“Yes?”

“Are we going to stay here until it goes off?”

“Yes,” said Lockhart, “I will. Someone has to make sure that it works.”

“You’re mad,” said Leni, “but I’ll stay too.”

“There’s no need,” said Lockhart.

“But…”

“No arguments! To work.”

For the next two to three minutes, they worked efficiently, if nervously. At one point, Pugh nearly dropped a canister, but saved it just before it fell. The chances were, said Lockhart, that it might not have broken, but it was just as well to treat the canisters as though they were crystal.

“That gunfire is getting louder,” said Leni.

“Ignore it,” said Lockhart. “Concentrate on this.”

Within another minute, they were halfway. Lockhart took a stick of explosive from his backpack, and, with trembling hands, set the fuse for ten minutes. There was no going back now, but he felt calm, in control. This was his job, his entire world. For the next ten minutes, he was no longer a husband, a father, an archaeologist—his only role was to destroy the sarin.

“Come on! Let’s pack the rest in!”

Their ammunition was running low, and the guards were attacking them with an ever-increasing ferocity. Marston and Simpkin had already been shot dead, and Strasser had to resort to throwing some grenades down the tunnel. He had not wished to, for fear of killing any of the prisoners, but there was now no choice. His decision was based purely on numbers—better for a few to die here than for millions to perish in London. Better for him to die as well, and he knew that time would soon come.

Within five minutes, they had packed the still with the remaining canisters. Now they simply had to replace the lid, and pray. The first few bolts went on easily, until they came to the eighth of the twelve. The wing nut wouldn’t twist down properly, as though the thread of the bolt had got mangled.

“What’s wrong with it?” Leni asked.

“The bloody thing won’t go on,” Lockhart grunted.

“Quick!” shouted Pugh. “We can’t have much more than two or three minutes!”

Lockhart ignored him and tried twisting it, but it wouldn’t budge. But for the want of a wing nut that worked, he thought, a city had fallen.