‘It’s made me take extra care when I go out,’ Sasha said. ‘I must have checked I’d locked the door about ten times before going out this morning.’

We went inside and watched the film. Halfway through I texted Charlie to say goodnight and to ask what she was doing.

She replied immediately. In bed, thinking about you. See you in the morning :) xxxxxx

‘Oh dear, you’ve got that look on your face,’ Sasha said. ‘Lovestruck puppy.’

And then she started to cry. I sat and held her for a while until she felt better, at which point she announced she needed to go to bed.

‘Thanks, Andrew,’ she said, as I left.

‘No worries.’

Her face was streaked with tears and there was a big damp patch on the front of my shirt.

‘You deserve it, you know,’ she said.

‘What?’

‘Happiness. I’m really glad you’ve met Charlie.’

‘Me too.’

She blew me a kiss and I started to walk home, my coat wrapped tightly around me. My flat was a fifteen-minute walk from Sasha’s.

I had just turned off the main road in order to take a shortcut through the quieter backstreets, when I heard footsteps behind me. I looked over my shoulder, a casual glance, and saw a figure in black, wearing a hood. The way they were walking – close to the walls, keeping in the shadows, their pace slowing as I turned to look – made me feel sick with nerves. I knew loads of people who had been mugged for their mobiles. It was an epidemic and I had just been walking blithely along the street staring at my iPhone in full view of any passing thief.

Or maybe it wasn’t a mugger . . . I couldn’t help but think of the person who had followed Charlie through the park, and the figure who I was convinced had been watching us that time by the lake.

I increased my pace, feeling in my pockets for weapons. I had my keys and I supposed my phone could do someone some damage if you hit them over the head with it in the right way. The person behind me – I pictured him as a muscular, wiry youth, the ‘hoodie horror’ who stalks middle-class urban nightmares – was gaining on me. I was only a few minutes from home now. I could be there in one minute if I ran. But what if the hoodie ran too and was much faster than me?

Heart thumping, I walked as fast as I could. I didn’t dare look behind me, as if doing so would invite the hoodie to jump me. I had no idea how close he was now. Maybe I should call 999, tell them I was being followed. But I clung to the hope it was all in my imagination, that the guy behind me was an innocent heading home.