Shortly, Grace could see a housing estate, and near it a cluster of industrial buildings. The landscape changed, rapidly, to an urban one – the edge of a town or city. He always found aerial views took a while to figure out, everything looked different and distant. But it was starting to look a little familiar as they passed over a large church or cathedral.

‘Recognize that?’ Potting exclaimed, his excitement palpable.

‘Chichester?’

‘Yes! Look at the date and time, top right on the screen!’

It read: Wednesday 8 May 3.24 p.m.

Grace felt a beat of excitement. This was the day before Stuie Starr’s body was discovered by his carer. The day on which, according to the pathologist, Stuie might have died. It fitted.

‘Keep watching, chief!’

More of the city appeared as the camera tracked over it. Then, suddenly, the image froze. It began zooming in on a particular area below, before it started moving again.

‘I’ve had Digital Forensics work on this all day, enhancing it,’ Potting said.

Grace could now see a garage, with a housing estate opposite. As the image was enlarged even further, he could make out what he was pretty sure was the Starrs’ house. A lone car was parked further down the road and, after the camera zoomed in further still, he could recognize the marque, a Mercedes, dark-coloured – either a C or E-class, he wasn’t sure.

Two figures, in hoodies, suddenly ran out of the house, sprinting away to the car. They looked furtively around, then jumped into the Mercedes and drove off at speed.

‘Norman, this is bloody brilliant! How did you get it?’

‘We didn’t have any luck from the aerodrome, but whilst I was out I passed a park in Chichester and saw people flying their drones. I went over and spoke to them and asked if any of them had been flying them on the 8th of May. They said they hadn’t but would mention it to other drone enthusiasts that they knew. One of them contacted me earlier today and produced this video. Sheer luck, chief.’

‘Excellent work, Norman.’

The video continued moving away from the house, in the opposite direction to the car, across the city, circling out over the harbour and the sea. Grace stopped and replayed the earlier part.

‘A local dealer’s confirmed the model as a current E-Class,’ Potting said. ‘I’ve had the ANPR team check all cameras in the Chichester area for an hour either side of 3.24 p.m. The gods are smiling on us, it was relatively light traffic. Just five of that particular model had pinged any cameras and only two of them dark-coloured. And here’s the bit you are really going to like, chief – one of them has a Sussex Police marker on it as being linked to a suspected armed drug dealer. Name of Conor Drewett.’