The headmaster extended an arm, directing them across the entrance hall and towards a doorway off to one side. The hallway was as impressive in its way as the building’s facade. There was a vaulted ceiling, and a thick green carpet running up a central oak staircase, with a gleaming gold carpet rod on each step. On the wall opposite the entrance, completely dominating the room, was a wooden engraving of the school’s coat of arms: a snake on one side, a dove on the other. Sicut serpentes, sicut columbae, read the Latin inscription – evidently the school’s motto.

‘I have to say, when news reached me about what had been found, I imagined sirens wailing and helicopters buzzing overhead,’ Harris said. ‘I am thankful that you and your colleagues instead opted to exhibit some discretion.’ His eyes dipped, as though he was taking in what Fleet and Nicky were wearing. He seemed to think they’d ditched their uniforms solely out of consideration to the school.

He directed them through the door, marked Staff only in gold-leaf lettering.

‘This is not the most direct route,’ the headmaster said, as he led them down a corridor in what appeared to be the administrative area of the building. ‘But at this stage of proceedings, it would not do to attract undue attention. In an environment such as this one, rumours spread quicker than measles. We’re already having to act to discourage some of the more gruesome ones. The line we’re taking with the pupils is that a site has been discovered of potential historical interest.’

They passed from the corridor into a kitchen, and a dozen workers dressed in white turned their way. Harris ignored them all, ushering Fleet and Nicky towards an emergency exit sign on the far side of the room. Fleet was beginning to feel like a call girl being smuggled through the back entrance of a luxury hotel.

The emergency exit took them outside, into a service area at the rear of the building. From here they could see the full extent of the enormous campus. There were football, rugby and hockey pitches off to Fleet’s left, all perfectly flat even though the campus itself was on a hill with the main building perched at the top. Thirty or forty metres down the slope, almost directly opposite them, was what was unmistakably the school’s chapel, although Fleet had seen cathedrals that were less impressive. Beyond the chapel was a dense line of trees, marking the boundary of a wood that seemed to stretch out of sight.

Harris was several steps ahead. He had veered from the path leading towards the chapel, on to the grass. ‘We’ll need to cut through the woods,’ he explained, as he waited for Fleet and Nicky to catch up.