They reached another door. Boggle went to open it and stopped. His hand was shaking where it rested against the scratched paintwork. He was steeling himself to carry on.

‘You see, when we first arrived here?’ he said. ‘The whole place was crawling with sickos. Reckon most of them were people who used to work here. We couldn’t clean half of them out. The place is too big. Is like a maze of corridors and hidden rooms down there. So we left them to it. Made all the galleries safe and locked the doors so that they couldn’t get up here where we were.’

‘You’ve been living with them underneath you?’

‘Yeah.’

‘How’d they get in and out?’ Blue asked.

‘Through the windows mostly. We do what we can, try and block any holes from the outside during the day, but they still get in.’

‘OK, open up,’ said Blue. ‘Let’s see what you got down there.’

Boggle did as he was told and the kids nervously headed into the stairwell.

Jackson, meanwhile, was leading her party up the main stairs, past the white marble statue of Charles Darwin sitting happily in his stone chair, oblivious to what was going on around him. Achilleus stayed next to her. He had a round shield slung across his back and carried a sharpened metal spike for a spear. The end had been broken and the shaft was scraped and dented. It looked like he’d recently been in a fight. He was as bashed about as his spear. His chin was cut and bruised, one ear bandaged, and there were spots of blood across the front of the old T-shirt he was wearing. It had a logo on it for the Sarajevo Olympics. He moved with some difficulty and was obviously in some pain. Despite his injuries, he carried himself with a certain confident swagger. He had a razor-cut pattern in his hair and was pretty well a textbook bad boy, the sort Jackson’s mother had always warned her about.

The sort she’d always liked.

They walked along the upper balcony, where the stuffed apes were. She expected some of the younger kids to say something, to make a joke, but she figured they were probably pretty spooked by the turn the night had taken. Only one of them spoke up, the little guy who was lugging the golf-bag full of weapons and who stuck close to Achilleus like a dog.

‘I never been here before,’ he said in a broad Irish accent. ‘I like animals.’

‘You come in here, they’d have to put you on show in a case, Paddy,’ said Achilleus. ‘With all the other monkeys.’

The little boy laughed.

‘That’s right. You said it.’

They soon reached the iron gates at the end of the balcony that closed off the minerals gallery. They were firmly closed and there were pale faces pressed up against the metalwork, fingers gripping the bars.