The Reform Club holds an annual lecture in memory of Lord Atkin, one of the few judges who has left an enduring mark on English law. Dauntingly, a dozen or more of his descendants (he had eight children) were in the audience when I gave the Atkin Lecture in November 2001. An attempt to say something not too solemn about precedent in the law, and something not too prickly about judicial activism, it has not been previously published except by the Reform Club as a booklet.

Professor Francis Cornford, whose Microcosmographia Academica sparked it off, held the Lawrence Chair of Ancient Philosophy at Cambridge which is now, by chance, occupied by my brother David. I acknowledge a debt not only to David's celebrated predecessor but – for the closing paragraphs of the essay – to my New Zealand colleague Ted Thomas.