‘I wonder if we could see it?’

‘I can’t imagine why you would want to, Mr Hawthorne. Nothing is the same any more. All the furniture was taken away … even the bookshelves. It’s been repainted.’

‘It still has the door.’

I could see that Helen Winters was regretting she had ever met us. ‘Well, all right,’ she said. ‘But I really can’t see how it will help you.’

She led us through the double doors and along a corridor decorated with the children’s paintings. As we went, I tried to cheer her up by admiring the artwork and talking about books. We passed the library, a bright space with miniature desks and beanbags. A plaque showed that it had been opened by Michael Morpurgo.

‘Such a lovely man,’ Helen said, a little caustically. The inference was clear. Unlike me, the former children’s laureate hadn’t come here investigating the half-forgotten death of the deputy head. ‘Have you met him?’

‘Many times. I’m a big fan.’

We reached her office – long and narrow, with papers piled high on her desk and certificates on the wall. The quiet room was next door. It had been modernised, carefully designed to soothe the more volatile children. Everything was soft: the sofas, the carpet, the beanbags, the stuffed toys and the lighting that faded from pink to mauve to green even as we stood there. One wall was covered with a mural showing an underwater scene and there were liquid lava lamps morphing away on low tables. Turning on the lights had also turned on music: the theme from the film of War Horse. Morpurgo’s fingerprints seemed to be all over the school.

‘This is where Major Alden worked,’ Helen said. ‘It was an office until I arrived, but we haven’t had a deputy head for years and I decided to adapt the room to its present use.’

‘Do you have a lot of difficult children here?’ Hawthorne asked.

‘We don’t consider any children to be difficult.’ Helen Winters replied in a way that suggested Hawthorne was once again straining her patience. ‘All young people need to calm down from time to time. Modern society can seem very stressful when you’re nine or ten years old. Children are under so much pressure these days. This room is a facility for everyone to use. I sometimes sit in here myself.’

Hawthorne had already turned his back on her. He was examining the door frame, which was unusually high. He opened the door and held it. I could see him working out how easy it would have been to balance the bust of Cicero above and for once I was sure we had both arrived at the same conclusion. There was no way one of the boys would have been able to set the trap on his own. They had to be working together. And the bust had a long way to fall. If the sharp edge of the plinth had been pointing in the right direction, it could easily have fractured Alden’s skull.