Aidan said he would take her and that he’d shower when he got back. Unlike my mother, he intended to go to work at the school.

Neither of us could hold back the tears as we said our goodbyes. I hadn’t seen Mum this distressed in a long time and it really got to me. But I was glad she was going to Ringwood. It was going to be a huge weight off my shoulders. She’d be perfectly safe there. I was sure of that.

After they’d gone I finished the coffee and did a quick tour of the house, checking the windows and doors. The place wasn’t as secure as it should have been. There was no burglar alarm. No motion-detector lights at the front and back.

The wall at the bottom of the small rear garden was only about five feet high and backed onto an unlit alley that ran between the houses.

Clearly I hadn’t paid enough attention to security and as a police officer I should have. I recalled that when we moved in the landlord had said that he was happy for us to install an alarm and outside lights. But we hadn’t bothered to, partly because we were never sure from one year to the next how long we’d stay. Our intention had always been to buy our own house or flat in a less expensive area.

As I stepped into the shower I made a mental note to arrange for a locksmith to come round at the weekend to make the front and back doors more secure.

We would also put up motion-detector lights that would come on if the man who had murdered Dave Prentiss and Marion Nash decided to approach our house.

Thunder rolled across the sky as I made my way into work. Rain showers lashed the streets, and I was forced to hail a cab from the tube station for the last leg of the journey.

When I walked into the office at nine o’clock it was throbbing with activity. A new whiteboard had been set up with photos of Mrs Nash and the crime scene in Clapham.

My stomach pitched when I saw the poor woman lying on the floor in a pool of her own blood.

‘I’ve never known anything like this,’ Tony Marsden said as he came and stood beside me. ‘We need to catch this fucker before we all end up like that.’

As sensitive as ever, I thought. But he was right. This couldn’t go on.

He looked at me and a line creased his forehead.

‘My money is still on Roy Slack,’ he said. ‘He’s the only villain out there who would dare to take it this far. We all know he thinks he owns this city and that he’s more ruthless than any of the other gang bosses.’