‘I honestly don’t know if these symbols are some kind of code, or incredibly advanced maths, or total rubbish. But Kaspar had one of the most creative scientific minds in Europe once upon a time. If anyone can work out what this is, it’ll be him.’

‘Thanks,’ Knox said. ‘I owe you.’

‘You owe Holland,’ White replied.

Knox slipped back through the old fire exit that connected the subterranean car park to the rest of Leconfield House. He’d temporarily relieved one of the custodians of the master key for the building’s emergency exits almost five years ago and made a copy. He’d been equal parts shocked and relieved to discover it still worked when he walked down the car park ramp ten minutes ago.

The car park smelled of old oil and stale air. He passed several grey and black Consuls, then the bays that housed the nicer cars of more senior officers. There were two empty spaces. One was his, which he’d never used—living in the centre of town, he saw no reason to own a car—the other belonged to Holland. At this time of day his dark green Bentley S2 should have been there, but it wasn’t.

Knox walked unnoticed back up the car park’s exit ramp and out into Mayfair.

When he made it back to Kemp House, there was another Watcher waiting at his front door. This one handed Knox an envelope, sneered at him when he asked what was in it, and stepped into the closing lift before Knox had a chance to say anything else.

Knox didn’t know if the silent treatment was just the traditional dislike Watchers had for their more menial tasks or a result of recent events. Given their low level in MI5’s pecking order, the Watchers shouldn’t know the details of Knox’s review board and suspension. But if there was one place gossip spread faster than the halls of Parliament, it was the corridors of MI5’s headquarters. And if there was one person in the Service the Watchers weren’t inclined to like, it was Knox. At the same time as Holland had been fighting to modernise MI5, Knox had made it his mission to retrain the Watchers, breaking them out of the stale techniques they used in their never-ending games of cat and mouse with foreign operatives. The Watchers considered themselves part of an ancient brotherhood and very much resented the interference from someone who wasn’t one of their own.

The envelope contained a preliminary autopsy report on the Italians, and it threw up about as many questions as everything else about their deaths did.