I nodded and he called for the bill. I offered to pay half but he shook his head.

‘It’ll be my turn next time, then.’

‘I’d like that,’ he said. We seemed to have passed the point where it was necessary to negotiate whether or not there would be another evening. In his quiet way, Mr Rainbird was just as confident as Jasper.

Outside there was still greenish-blue light in the sky and I could hear the last calls of birds going to roost in the trees of the green opposite Casa Flore. It was mid-June, another warm city night.

‘Come and look at something,’ Mr Rainbird said. He crooked his arm and without thinking I slipped mine through it. He wasn’t much taller than me and we walked easily in step, shoulder to shoulder.

He guided me through the traffic and we crossed the corner of the green, then turned down a street diagonally opposite. I was thinking of all the similar little networks that made up London’s vast nervous system, when Mr Rainbird stopped at the entrance to a narrow alley. There was a tall iron gate blocking the alley itself, but another one just wide enough for pedestrians stood open at the side. He stood aside to let me through. On the other side of the gate I felt the pressure of cobblestones through the thin soles of my shoes.

I had known about this turning, of course, and had glanced down it in passing, but this was the first time I had walked along here.

There was a perfect double row of tiny houses, each with its miniature square of front garden separated from the alley by a low wall. The houses had little gables surmounted by Gothic lace ironwork and the tiny double bay windows were capped with an exuberant finial of wrought iron. Down the centre of the street stood a row of lampstands with curved brackets and iron stems twisted like barley sugar. The gas mantles had been replaced by electric bulbs, but their light was still appropriately yellow and dim.

I knew that these were almshouses, built a hundred and fifty years ago by a philanthropic Victorian ironmaster for poor but virtuous women of the parish. It wanted only a few inches of snow to make the perfect Christmas card scene. The white flowers of nicotiana and tumbling Iceberg roses shone through the dusk instead and I half closed my eyes to make snow of them.

We walked slowly to the end, admiring the perfection.

‘How many poor but virtuous live here now?’ I wondered. The alley was gentrified to the point of caricature and the almshouses probably changed hands for half a million apiece.

‘Oh, I expect there may conceivably be virtuous lawyers and television executives and bankers.’ Mr Rainbird laughed. ‘But definitely no poor ones along here.’