‘Iain,’ he said, ‘get on the phone to every section officer in New London and order them to inspect their areas fast. I want the HPFC searched, I want every room the rebels have ever visited to be turned upside-down, I want vehicle ports torn apart and every officers’ sector gone over inch by inch. Nathaniel, load up some security files and find out which of our rooms were targeted around Christmastime.’ He flashed a proud pair of shiny blue eyes towards his twitching prisoner. ‘And thanks for giving that part away, you old fool.’

A phone rang on Marshall’s desk. Marshall jogged across his office and answered. Sadly, the conversation did not take much time.

‘Nick,’ said Marshall, ‘the Perimeter Point has been replaced.’

Nicholas Grant laughed, lifted the plastic cover at his side and rested his fingers on the black computer switch.

‘Dr McCormick,’ he said, ‘it’s a beautiful coincidence that you’re here to watch my empire become utterly invincible – and all before your secret weapon had any chance to make a difference. Iain, turn on your TV. I want to see a security feed to the outside of the Citadel. It’s a shame we’ll be indoors for the man-made northern lights, but watching my victory on television will have to do.’

Marshall obeyed, and flicked around with his remote control until he found a video feed from the upper battlements. The view stretched across the English countryside, soon to be as isolated from New London as Sydney Opera House.

McCormick looked back at Nicholas Grant, just in time to see him flick the switch and activate the AME shield.

Chapter 25

McCormick had never been keen on videogames, but he had seen the ‘undeserved death face’ in plenty of children whose characters had unexpectedly got shot or fallen from high platforms. When the switch was flipped and nothing changed on Marshall’s enormous computer, Grant mirrored those children’s expressions perfectly.

‘What the hell do you mean “coordination error”?!’ he screamed, droplets of saliva landing on the offending screen. ‘I just bloody replaced the Perimeter Point!’

McCormick could not hide his smile. Grant started to pace around the borders of the room, looking for something on his three-walled computer that would make everything right again. Unsuccessful, he glared at McCormick, his neck and shoulders trembling. McCormick decided to speak before somebody forced him to.

‘I may be a mathematician,’ he said, ‘but I know a thing or two about physics. And it looks like you organised your circuits in series instead of parallel. Maybe you had to, given the nature of the shield and how it depends on every single coordinate working. But it means your Perimeter Points are like Christmas tree lights: once the circuit’s broken, you can’t tell how many are faulty at the same time. I imagine you’ve worked out where I’m going with this.’