James had heard him walking around and then he had glanced into the stall. James caught a brief glimpse of his wiry, grey hair and pale skin before he coughed once more and went on his way.

Since then James hadn’t been disturbed and now he was able to use this secret route out of the building whenever he needed to.

Under the floor was a crawl space just large enough to fit his slim body into. He passed the boards down, lowered himself in after them and replaced the tiles above his head.

He could now risk using the torch. He switched it on, illuminating a tiny passage that ran along the entire length of the building between the joists. It was filthy and dusty and laced with blackened cobwebs. He shuffled awkwardly forward on his belly, trying not to make too much noise. Above and below him were sleeping boys, but if they’d ever heard anything they’d kept quiet about it.

James crawled along until he was directly beneath the locked storage room at the end of the corridor. He remembered the night he had first got this far, and how relieved he had been to discover that several of the floorboards were loose and rotten. It had only taken him a few minutes to prise two of them free. Now he simply pushed them out of his way and wriggled up into the room.

He replaced the boards, stood up, knocking the dust off his dark clothes, and sneezed. Nothing had changed in here since his last visit. The room was piled high with forgotten school junk: broken tables and chairs, rotting camp beds, prehistoric sports equipment and boxes of yellowing books and papers. There was a tiny window in the roof, so encrusted with dirt and dust and birdlime that it barely let in any light at all. James climbed on to a pile of boxes and forced the rusted latch open. Then he folded the window back, grabbed hold of the edge of the frame and hauled himself up. In a moment he was out on the roof, in the fresh air, with the whole of Eton spread out beneath him.

It was a beautiful clear summer’s night and the moon was nearly full. James could see over the rooftops down to the river Thames and across to Windsor Castle on the other side. It was close to midnight, but there was still some activity on the streets, the odd car moving about, lights in windows, a barge going upriver towards Maidenhead.

James had planned carefully for this. He had noticed that the storage-room door never seemed to be opened, and, just to make sure, he had fixed a hair across the keyhole in the padlock, sticking it in place with two tiny dabs of grease. A week, two weeks went by and the hair was undisturbed. A quick check outside had shown him the window and a possible way on to the roof, so then he only needed to work out how to get into the room. Spotting the space beneath the floorboards when a leaking pipe was being repaired in the washroom had solved that problem.