It’s increasingly the tendency of lobby journalists to deploy violent imagery to describe the manoeuvrings of our political class. Cast your mind back to the recent European elections, described as a “bloodbath” for Labour, and the drama over the leadership of “street fighter” Gordon Brown. But in 1809, politicians actually did try to kill one another – namely Viscount Castlereagh and George Canning, who fought a duel on Putney Heath that left the latter with a wounded leg. It’s that event to which the title of John Campbell’s book on political rivalries, Pistols at Dawn, refers; though none of the other feuds is as violent, most are at least as bitter.

Politicians who accuse the media of being obsessed with personalities should read this book – it’s not just the media who have that problem. In 1974, Margaret Thatcher went to Edward Heath’s Commons office to tell him she intended to challenge him for the leadership of the Tories. “You’ll lose,” he told her, abruptly. He lost, and they were practically the last words ever spoken between the two. Although Heath and Thatcher were never close personally, in two of the case studies Campbell examines – Asquith and Lloyd George; and Blair and Brown – the enmity seems to have been exacerbated by genuine warmth, or least mutual admiration, gone wrong.

Although the Labour government managed to survive the convulsions of the Blair-Brown wrangling, it hardly did much good for the functioning of the administration. As for the rivalry of Asquith and Lloyd George – that contributed to leaving the Liberals out of power for 87 years, and counting. This book serves as a powerful lesson – one which Labour MPs might do well to remember – that bitter feuds sometimes serve the interests of individuals, but rarely those of parties.