I made some quick decisions. From now on, the girl would stay 24/7 at my house and Matt would look after her. This meant that, thank God, he took care of her during her "episodes." Our old address just became a mailbox for admin.

But we needed a new office: not so much that we actually needed one, but we had to give the guys that torched the warehouse a wide berth; they wouldn't hesitate to kill or kidnap the girl, or worse, make her work for them if they learned how we'd got our 200-digit prime.

I also wanted to clear something up, and at the next meeting with my client, his face betrayed everything. He handed me the papers for the 155-digit prime, but I didn't care about that. I asked him if, by chance, he told other firms about our activities.

He relaxed and tried to smile: "Well, of course. There is only one company around doing the same thing as you: MegaPrimes. But you already knew that. I tell MegaPrimes each time you bring us a number for three reasons, which I'm certain you'll agree with.

"The first reason is that since we're the buyer, and, moreover, because we buy on behalf of the Treasury, we must buy for the right price. Your recent performance allows us to put pressure on MegaPrimes. But we'd put equal pressure on you if the situation was reversed.

"The second reason is that your business, as I've already told you, serves a greater purpose – giving us a strategic advantage in trade security. And competition improves performance. We're quite happy with the existence of Prime Numbers, Inc., because MegaPrimes can no longer lie back in its chair waiting for the bills to be paid... Both of you get up in the morning and ask yourselves, 'How can I be stronger than my rival?' By asking this question you are serving the nation.

"And the last reason... The government holds a 20 percent stake in MegaPrimes. It's another way of saying that 20 percent of subsidies return to the government at the end of the fiscal year."

Well, a completely different way of saying it was that any move I made was reported to MegaPrimes. This bastard had sealed everything tight; he'd been playing ten steps ahead of me.

But he only had pawns, whereas I had the queen.