She stopped dead and grabbed both my hands. ‘Oh my God. I’ve just thought! We could try to have lunch at Brown’s. I used to love Brown’s! I haven’t been there for years! Come on!’ She pulled me down a side street. ‘If I remember right, it’s not far!’

And she was right: Brown’s was lovely, and the theatre blew me away and, with Grace at my side, I began to think that maybe I could ‘do’ Central London after all, if I was careful, if I was with someone. But, as we threaded our way back to Charing Cross after the show, we saw, up ahead of us, a knot of people gathered on the pavement. As we drew closer, I saw that some of them had their hands over their mouths; others had their phones pressed to their ears; a couple were shaking their heads. A man was kneeling on the ground near the back of a bus, which I realized now was unnaturally still, the engine off and the driver pacing helplessly nearby, his hands tearing through his hair. The traffic lights moved robotically through their cycle but the traffic didn’t move. Shock echoed in the air.

‘Something’s happened.’ Grace peered forward, straining towards the scene. Dread pushed upwards from my stomach; my hands suddenly cold and clammy inside my gloves.

‘It looks serious,’ I said. ‘Maybe we should…’

‘I don’t see an ambulance. No paramedics,’ Grace interrupted. Her tone was brisk. Professional. ‘Whatever it is, it must have just happened. They might need me.’ She broke into a run.

‘Grace…’ I said. My legs were weak and my breathing shallow. Heat flooded my face and I swallowed. Already I’d clocked the distant wail of sirens. We should turn back, I wanted to tell her: go a different way; let the emergency services deal with whatever it was that had happened, but this is what Grace did. This was her thing. I followed as she hurried towards the scene.

‘I’m a doctor! Let me through!’ Grace shouted, twisting her way through the onlookers. At the kerb, she paused for a second and took in the scene then, within moments, she threw her handbag down and was on her knees close to the rear wheels of the bus.

I shouldn’t have looked. It was my mistake. I should have turned and walked the other way. I should have sat in a pub or stood in a shop; I should have done anything but look. I saw the bicycle bent out of shape. I saw the leg protruding out from under the bus. A woman’s leg, bent at an unnatural angle and deathly still, the trainer on the foot a shocking pink that stood out against the black of the tarmac. I saw the look on the faces of those standing watching.