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In compiling the annual list of the 100 most influential people on the Left or Right of British politics, we came very close to putting someone whose identity we do not know at number 2 in both lists. We will call him or her “Deep Moat” – the Whitehall whistle-blower who shook British politics to its foundations by leaking the entire database of MPs’ expenses claims, published by the Telegraph.

Even before that expenses scandal, David Cameron was doing well as leader and as a prospective prime minister. But then a pretty good year turned into what is likely to be the year before he becomes prime minister. Of course, anything can happen in politics and there is still some time before polling day, but the election is...