Pistols at Dawn, By John Campbell

"Pistols at dawn" is a more literal title for a book about political rivals than you might imagine: two of the combatants profiled here, Viscount Castlereagh and George Canning, really did draw pistols against each other – the only pair, John Campbell notes drily, "to have actually tried to kill each other".

The complex ins-and-outs of political manoeuvring might test even the hardiest of readers here (I almost gave up during the chapter on Aneurin Bevan and Hugh Gaitskell), but it's well worth staying the course. The question of whether all the best leaders need an equally great rival beats throughout this history, which reveals just how close rivals often are: sometimes they are mentor and protégé, as was the case with Charles Fox and William Pitt; sometimes they are members of the same party, as were Asquith and Lloyd George, whose rivalry emerges only in response to events such as a world war. And sometimes, of course, they began as friends, as Blair and Brown did.

Campbell's dissection of this last union covers much familiar ground, but he shows just how much a close political relationship can hobble an administration as much as energise it, and the truth in Thomas Grenville's maxim, "When two men ride a horse, one must ride behind."