Ewan could barely feel the organs inside his chest. Adolf Hitler with atomic weapons would have been less dangerous than a dictator with this technology. If Grant had his way, the same kind of shield would surround the whole of New London, and in time his other Citadels too, rendering him invincible forever.

Ewan reached for his assault rifle.

He released a flurry of bullets into the glass wall. The glass did not shatter, and the bullets only produced a couple of spider-web-shaped cracks. Clearly the chamber’s glass was bulletproof.

Bullet resistant, not bulletproof, Ewan corrected himself. No glass is perfectly bulletproof. You just have to get creative.

Ewan put his brain into gear. When it came to non-academic tasks, his brain was a formidable weapon. At that moment, it was remembering a school trip to the Roman walls at St Albans, back when he had been allowed on mainstream school trips. The tour guide had shown him a legionary’s sword – a gladius, if he remembered right – which had a little steel stub at the end of the handle. It was for braining enemies who got too close, by thumping the handle onto their head where the tiny stub would crack through their skull. The full force of a Roman’s arm would be concentrated into a square centimetre, and the results would be devastating.

The glass could be broken. Ewan just needed a gladius.

The butt of his rifle made a fine handle, with a flat enough surface to attach some kind of stub. He reached to the corner of the nearest window pane and peeled off the adhesive warning sticker, rolled it backwards over itself to make it sticky on both sides, and placed it across the rifle butt.

On the desk at his side, some smart-arse scientist had left his coffee mug behind – one that literally read ‘smart-arse and proud of it’. He grinned, and wondered whether that scientist had been smart enough to know a little fact that Ewan had learned via YouTube: that ceramics were great for smashing windows. He threw the mug to the floor, and picked through its shattered remains. He stuck a promising-looking piece to the butt of his rifle, and after three hits from his makeshift gladius the entire pane of glass shattered.