‘Okay,’ she said and checked the time on her phone. It was almost ten o’clock ‘Can I go now? I’ve hardly got any food in the house, and I haven’t ironed anything for my first day’s work. I’m horribly behind.’

He gave her a steady stare. She had the kind of face that made it easy. ‘Sorry, Kirsty, I need half an hour more of your time. There’s a good chance the murder weapon is somewhere nearby, and having you with me will give me a better chance to find it. So if you don’t mind, I’d like to go back to the scene now and join the half-dozen officers who are already there.’

‘Okay,’ she said quietly.

Gillard smiled. ‘I promise that when we’re done I’ll give you a lift to the supermarket.’

‘And the ironing?’ She grinned.

‘Don’t push your luck.’

She laughed. Gillard decided that he liked her.

DCI Gillard wasn’t exaggerating in his praise for the young investigator. There were so many things she could have done wrong, but hadn’t. She hadn’t put her own footprints into the crime scene, she hadn’t touched the body herself, she’d attempted to photograph the tyre tracks and footprints, and she had restrained the dogs. Using the pizza box to hold a crucial sample of snow was an act of genius.

Back at Ashtead Common the corner of Woodfield Lane was a hive of activity. An articulated low loader carrying a large white Portakabin was just reversing in through the open vehicle barrier, guided by one of the Ashtead Common rangers.

‘That’s our mobile incident room, God help us,’ Gillard said to Mockett. ‘It’s universally known as the Khazi because of the smell.’ He recalled many long hours in its stale air, listening to officers come and go through the squeaky plywood door, and trying to make himself heard over the drone of the extractor fans. Black mould grew readily on its institutional off-white paint, however many times it was washed with fungicide.

The crime scene was marked by half a dozen police vehicles, a large white CSI tent, and an encircling loop of crime tape which fluttered in the breeze. Though it was by no means warm, the temperature was several degrees higher than it had been when the body was found and only the vaguest traces of slush could still be seen. Duck boards had been laid across the damp grass to allow vehicles to come and go across the 200 yards to the edge of the tape without churning up the turf. That had been insisted on by the City of London Corporation, owner of this precious piece of green space so close to the metropolis.

Gillard was greeted at the edge of the tape by a uniformed PC, and then by a woman in a crackling plastic Tyvek bodysuit. It was DI Claire Mulholland, Gillard’s protégé. He introduced her to Kirsty Mockett and then asked, ‘Any luck finding the murder weapon?’

‘Not so far. Based on photographs of the wounds, Yaz reckons we’re probably looking for a hammer, or something similar. Certainly something with quite a bit of weight.’