I can recall clouds of sparrows rising up in the fields behind my suburban childhood home on the edge of London. But by the late 1990s they had simply vanished from many of their former haunts.

London was the worst hit: during a survey of Kensington Gardens in 1925, the ornithologist Max Nicholson counted more than 2,600 sparrows, but when he repeated the count at the turn of the millennium he found just eight. Even in the late 1960s, sparrows were so common in the city’s parks that I have a photo of the birds perched on my outstretched hand to feed. Now, you are lucky to see them anywhere in the capital.