The government’s Research Excellence Framework (REF), which determines the allocation of research funding to British universities, tends to reward microadvances in each field. These usually take the form of articles published in the top peer-reviewed journals, particularly in the USA. This suits some disciplines better than others. When I was director of the London School of Economics, the historians there often complained that long books summarising big themes for a general audience became rarer as a result. They had a point.

The consequence is that broad-sweep surveys are now typically produced either by historians who have decided to make their own way outside academia or by retired professors who have stepped off the promotion treadmill and no longer need to count citations or try to measure their ‘impact’ (now the favoured