In the spring of 2021 I took a man to a pub in Hackney and bought him a drink. Perhaps he should have been doing the buying, since I had just handed him a large sum in return for his narrowboat. But I was in an exultant mood. No London flat, I reasoned, could ever be as cosy as that low-ceilinged, teak-panelled interior with its coal-burning stove and narrow cabin bed.