If only one crucial detail in history had turned out differently… such is the premise of many a work of fiction, especially counter-factual histories and time travelling science fiction tales. Yet for all the popularity of the well known piece of verse, “For the want of a nail the shoe was lost…” which culminates in a kingdom being lost, serious counter-factuals by experts in a field are rather rare.

Those who see themselves as proper academics have often looked down on counter-factuals as light entertainment for the not-so-serious, missing that, as The Guardian’s review of this book put it, “It’s only when you consider how to manipulate the conditions to create an alternative future that the factors that shape outcomes become clearer”.

So Francis Beckett’s collection, The Prime Ministers Who Never Were, is a welcome publication not only for adding to small collection of British political counter-factuals but also for having such a heavyweight list of contributors.

By focusing on senior politicians who never quite made it to 10 Downing Street, this collection benefits from being mostly dependent on tiny twists in fate which it is extremely easy to imagine having happened – a slight shift in MP votes in a leadership election or a sudden death that did not occur. It is a serious collection with serious tales, but some authors let a little light mischief slip into their stories as with the idea of a Tony Blair Home Secretary under Prime Minister John Smith being wheeled out to dismiss as vacuous the “Third Way” being pushed by opposition leader Michael Portillo.

Historians and others perennially debate how much influence individuals can really have on events in the face of bigger forces, and these chapters do a good attempt at making the case. In particular, the fact that Halifax almost certainly could have become Prime Minister in 1940 if he had really wanted to, but instead at a crucial meeting with Neville Chamberlain and Winston Churchill did not press his own case, makes for a fascinating what-if from Hugh Purcell. Even Churchill, one of the figures most likely to be put in the “big enough character to change events” category was subject to such small twists of fate.

Many of the chapters take familiar what-ifs – what if John Smith had not died suddenly, what if the Tories had won a handful fewer seats in 1992 and so on – but there are also some strikingly original ideas, including Peter Cuthbertson’s story of Mrs Thatcher anticipating her demise and campaigning successfully to be succeeded by Norman Tebbit.

The subtlety with which events are initially shifted in these counter-factuals is both a strength – it makes the exercise of pondering “what if.” all the more poignant and insightful – but also a weakness, at least for the non-expert reader. Unlike volumes such as President Gore… and other things that never happened (to which I contributed a chapter on the 1832 Great Reform Act), this volume does not provide any commentary on what has been changed in the alternative histories. If you are not familiar with the details, where facts stop and fiction starts is easy to miss in many cases so whilst you enjoy reading this book, having some reference books or the internet to hand may well enhance the enjoyment.