In London Bridge Is Falling Down: A Peculiar Crimes Unit Mystery (Bantam, Dec.), Fowler wraps up his series featuring oddball British cops tackling oddball British crimes.

Why end the series?

I’d planned to write one murder mystery, not a series of 20 books, particularly as I was writing standalone fiction and nonfiction at the same time. During the pandemic, I went for a Covid test, and was diagnosed instead with terminal cancer. Mortality concentrates the mind wonderfully, and so I’ve become extremely productive lately. Still, it played a big part in the decision to end the series.

Are there real-life inspirations for the two mysteries, the shut-in whose death may have been the result of foul play and the hit-and-run fatality?

For the first, it was the kind of “Where Social Services Failed” story that hits the press again and again. When your friends move away, growing old alone gets tough. The elderly fall prey to the unscrupulous. This novel also references the ongoing case of a diplomat’s wife who accidentally ran down a young man, killing him, and then fled to the U.S.

What about London has most surprised you during your decades of research into its history?

Its incredible resilience and consistency. You think certain things have gone for good, and it turns out they haven’t at all. Much has stayed the same, and London characters continue to evolve. Their strangeness is still there; now it’s just a different kind of strangeness. Take my downstairs neighbor. She makes organic nuts, translates manga, and is a weight-lifting champion. People are freer to do what they want.

Are there recurring themes that you’ve integrated into the mystery plots?

I live on the roof of a converted warehouse in the center of London, within sight of St. Paul’s Cathedral. Our building was always full of crazy old hippies who bought their apartments cheaply decades ago, but now they’re being forced out and replaced with the invisible rich. I hate this change in London; it’s a recurrent theme in the books. Cold corporate hands have wiped away much that was messy and independent about the city. For example, we think of Belgravia as a soul-dead neighborhood containing embassies and grand houses nobody lives in. But, until the early 1960s, it was just a London neighborhood with cleaning ladies and milkmen and kids playing in the street. Another major theme of the books is that our national problem is not race but class—something our government has done nothing to dispel.