The smokers’ patio was directly above the first-floor dining room, though the unit was built on a slope, so it was only one-and-a-bit storeys to the ground. It was a grim space, with mildewing plastic chairs and grey streaks where rain had flushed the ashtrays.

Julius hoped the area would be empty, but half-eight was a nicotine addict’s last chance before morning and a dozen teenaged patients sat chatting, or leaned on metal railings, releasing plumes of smoke into a dramatic orange sky.

‘There’s a ledge at the end,’ Alex explained, pointing past an anorexic girl in a wheelchair. ‘It’s not much of a drop with your height. The vehicle gate is controlled from inside, but shift change is nine thirty, so staff will be coming and going in their cars.’

‘Is there a camera covering the gate?’ Julius asked as he stepped past the girl in the wheelchair and sized up the drop.

‘Almost certainly,’ Alex said. ‘But it’s not like that receptionist stares at the monitors the whole time. The staff always have a battle clearing smokers off the patio by nine, so they’ll be out here any minute. If I were you, I’d drop now. Squat in the bushes, then sneak out the first time the gate opens after proper dark.’

Julius felt his foot touch the ledge over a window and scraped rust as his hands slid down the metal bars. He’d hoped to dangle and drop from the ledge, but there was nothing to grab, so he had to jump.

Pain shot up one ankle as Julius landed in grass soft enough to give way and soggy enough to feel water seep through the knee of his jeans. He spun around and saw a dining-room window level with his shoulder. A cleaner was mopping inside, but the salad bar screened Julius as he edged around and squatted behind prickly holly bushes.

The sunset had gone grey, but it still wasn’t dark. Alex had suggested he wait, but at least five people had seen him drop, and with half the kids in the Freeman Unit off their head on psych meds, there was a chance someone would blurt.

The short stretch of grass between the building and vehicle gate hadn’t been mowed through the winter. It squelched and tangled as Julius sprinted over, then stumbled on the root of a huge tree that made a perfect hiding spot close to the gate.

After a three-minute wait, he darted from behind the trunk as a cleaning contractor’s van drove through the electronic gate. He was almost through when he had to dive into the wet grass. A second car was going fast, trying to catch the gate before it closed.