Britain has imported yet another American cultural norm. As of last week, our leading politicians are expected to publish their tax returns. The story of how this development came about is not an edifying one and, in retelling it, I hope to persuade at least some American politicians to reconsider the tradition.

It all started with the leak of the Panama Papers. Among the hidden slush funds was one company that was wholly innocuous, except for its chairman’s surname. It turned out that the late father of the British prime minister had run a fund based in the Bahamas.