An area of nearly two thousand square metres had been cordoned off, away from the eyes of the public. The path was loose, chalky gravel giving way on one side to the bulrushes of the canal, on the other to a tangle of undergrowth – cow parsley, nettles and grass. Officers had left a gap of about fifty metres between the screens and the inner cordon, limited by police tape. Thirty metres or so past that, in a part of the undergrowth that formed a natural tunnel, stood a white tent.

Zoë and Ben pulled on white forensic suits, tightened the hoods, and added gloves. They ducked into the tent. The air inside was warm and packed with the scents of crushed grass and earth, the ground crisscrossed with lightweight aluminium tread plates.

‘It’s her.’ The crime-scene manager stood a foot inside, making notes on a clipboard. He didn’t look up at them. ‘No doubt. Lorne Wood.’

Behind him at the end of a walkway the crime-scene photographer was circling a muddy tarpaulin, taking video.

‘The tarp’s the type they use to cover firewood on the barges. But no one on this stretch of canal is missing one. The guy threw it over her. To look at her you’d think she was in bed.’

He was right. Lorne was lying on her back, as if asleep, one arm resting on top of the tarp, which was pulled up to her chest like a duvet. Her head was lolling to one side, turned up and away from the tent entrance. Zoë couldn’t see her face, but she could see the T-shirt. Grey – with ‘I am Banksy’ across the chest. The one Lorne had been wearing when she’d left her house yesterday afternoon. ‘What time was she reported missing?’