A friend of mine turned up in the pub last night after an absence of several weeks. He and his wife had been on holiday in Porto – a city I have never visited – and I was intrigued to learn how their trip had gone. “How much time do you have?” he asked me – never a good sign. I pointed to the full glass in front of me on the table.

Anyway, it turned out that Porto is extending its metro system so that the area around their hotel was a building site. “It was hard to walk anywhere without detours. The air was full of cement dust. And then I developed acute gout combined with arthritis, which was really painful. Finally, I fell down the stairs. It was a complete disaster.”