‘OK,’ McCullough said, pulling a set of latex gloves out of her pocket and handing them to Hanson. ‘You two may as well look too. Any scuff marks, dropped items, signs of discolouration of the soil or obvious blood on the grass or paving, call me over.’

So Hanson and Lightman began treading the frozen grass, stepping slowly and carefully. They moved in and out of the sunlight between the trees. It was strange how quickly they got into a soothing rhythm, despite the freezing air. There was nothing to do except look at their feet and make occasional remarks.

When she glanced over at Ben a few times, she realised that he looked less neutral than usual. There was an aura of brooding about him.

‘You aren’t beating yourself up about Niall Reakes’s flights, are you?’ she asked him, quietly. ‘If you are, you’re being an idiot.’

There was a note of surprise in his expression as he looked at her, and then he gave a very small smile. ‘I’ve never denied being an idiot.’

‘You spoke to the conference organisers,’ Hanson said. ‘You spoke to the airline. It’s not your fault they hadn’t bothered checking properly.’

‘But I always work on the assumption that people don’t bother,’ he said, with a shrug. ‘It’s how I make sure of things. And I should have chased them up.’

‘It didn’t make any difference,’ Hanson told him. ‘Niall Reakes is still going to have to explain himself. So cut yourself a bit of slack. Otherwise it makes the rest of us feel worse.’

Ben’s smile turned into a laugh, and she was pleased to note that he seemed a little less morose as they trod onwards. It made her feel incrementally more useful and in control of things, and that was important right now.

After ten minutes, Lightman found an empty cigarette packet in a patch of remaining snow. Linda came over and bagged it up, despite the low chance of it meaning anything. Five minutes later, Linda’s team found a single glove that looked like it might belong to a woman. It was navy fleece, the cheap kind you got in petrol stations, and it was sodden with melted snow. It got bagged up too.

A few minutes later, at a midpoint in the green, Hanson caught a glint of reflected light. Crouching down, she saw an earring nestled into the grass. Its triple rows of hanging diamantés were set into silver squares. It looked, to Hanson, like the sort of thing Louise Reakes might well have worn on her night out, and she tried to remember whether earrings had shown up on the CCTV.

Lightman stepped carefully past her where she crouched, and then stopped.

‘There’s blood,’ he said.