Few who witnessed it will forget the euphoria that swept France on 10 May 1981 when François Mitterrand was elected president of the republic – it was over a quarter of a century since a left-wing president had held power in France. Yet Mitterrand was not a typical left-wing leader. He had belonged to the extreme-right-wing Croix de Feu in the 1930s. As justice minister in the 1950s he sanctioned the guillotining of 45 Algerian rebels. And as president he annually sent a wreath to the tomb of Marshal Pétain, the head of Vichy France. He has often been described as Machiavellian and Sphinx-like; shortly before he died in 1996 it was revealed that for years he had lived a double life.

Philip Short is therefore on to a good thing when he frames his work as a ‘study in ambiguity’. For who in fact was François Mitterrand? Was he a conformist or a nonconformist? During the Second World War, was he a resister or a collaborator? Was he a man of the Left or the Right? Was he principled or unprincipled? Was he a visionary or a man of his times? Was he a success or a failure?

This is not the first book on Mitterrand, about whom studies were being written even during his 14-year presidency. There are good political profiles such as Alistair Cole’s François Mitterrand: A Study in Political Leadership (1994), Ronald Tiersky’s François Mitterrand: The Last French President (2000) and David S Bell’s François Mitterrand: A Political Biography (2005), but these say relatively little about his private life. Short was the BBC’s man in Paris in the 1980s and interviewed many of the leading politicians of the era. After writing biographies of Mao Zedong and Pol Pot, he returned to France and this time the women counted for more than the men. He interviewed Mitterrand’s wife, Danielle, and, even more adventurously, Mitterrand’s ‘other woman’, Anne Pingeot. The result is a fascinating interweaving of the public and the private and a valiant attempt to get to the heart of a man who famously kept at arm’s length all but a close circle of friends.

So was he a conformist or a nonconformist? Mitterrand was born in 1916 into a conventional Catholic provincial background in southwest France, not unlike that portrayed in Mauriac’s Thérèse Desqueyroux (1927, now a film by Claude Miller). Since cognac production was monopolised by a clan of rich Protestant families, Mitterrand’s family made vinegar. A student in Paris in the 1930s, Mitterrand was of the generation born during or after the Great War who, feeling that the victory had been squandered by a descent into corrupt parliamentary politics and the threat of Bolshevism, joined extreme right-wing or fascist groups. They were later termed ‘the nonconformists of the 1930s’.

Mitterrand failed to qualify as an officer and fought in the disastrous war of 1940 as an NCO. He was not sad to witness the demise of the Third Republic that fell with France, and he became one of nearly two million French POWs held in German camps. At the third attempt he escaped back to France, where he helped organise former POWs and represented their interests in the Vichy government. As the tide of war turned towards the Allies he moved his POW organisation into the resistance camp. This said a good deal about his politics: he played his cards very close to his chest, appearing obedient to the Vichy regime while working in secret with the Resistance; but even after the demise of Vichy he was unable to sacrifice his loyalty to the father figure Pétain.

After 1944 Mitterrand became the quintessential politician of the undistinguished Fourth Republic. The small party he helped to found was a pivot between Left and Right; he was elected deputy of the rural Nièvre on a cocktail of anti-communist votes. He became a minister 12 times but never prime minister. When his chances of this were ruined by de Gaulle’s return to power in 1958, he set himself in opposition to the general and wrote a tirade against what he viewed as a coup d’état and an assertion of personal power. He defined himself as anti-authoritarian and moved towards the Left. In 1971 he became first secretary of a reinvented Socialist Party, started to read Marx and built a ‘union of the Left’ between socialists and communists. It is not clear, however, whether this conversion was principled or merely the fruit of ambition, fashioning a vehicle that in 1981, at the third attempt, would take him to the presidency. In 1972 he had confessed, ‘I will die a liberal’; within two years of coming to power the ideology of a ‘break with capitalism’ had been ditched for one of cuts and modernisation. He had embraced the communists the better to stifle them.

Was Mitterrand a success or a failure? He introduced a slew of reforms, from a reduced working week and a fifth week’s paid holiday to decentralisation, equal opportunities for women and the abolition of the death penalty. For two spells, after the socialists lost their parliamentary majority, he worked well enough with governments of the Right – those of Jacques Chirac and Edouard Balladur – in what has been called the ‘Republic of the Centre’. Short is less interested in this than in Mitterrand’s foreign policy forays: bringing the USA back from the brink of nuclear war in the early 1980s, containing a reunified Germany within a stronger European Union and flying to besieged Sarajevo in 1992 to open the way for UN peacekeeping.

But whether Mitterrand was a statesman or just a politician remains unclear. One of Short’s most tantalising quotations is from Jacques Chirac on the evening of Mitterrand’s death in January 1996, when he said that Mitterrand was the ‘reflection of his century’. He might have developed the point to argue, perhaps, that while de Gaulle was a visionary who made France, Mitterrand only mirrored it. De Gaulle dragged France from the jaws of defeat in 1940; Mitterrand presided over the decline of a middle-sized power. Mitterrand held on to the French empire in Algeria well past its sell-by date; de Gaulle jettisoned it in favour of Europe and economic modernisation. De Gaulle founded the Fifth Republic as a regime with a strong executive; Mitterrand criticised it before discovering that it fitted him like a glove.

The great asset of this book is the combination of the political and the personal. Giscard d’Estaing taunted Mitterrand in a televised debate in 1974 that he did not have ‘a monopoly of the heart’. Short shows us what sort of heart that was. Three women dominated his life: 17-year-old Marie-Louise, whom he met when he was a student and to whom he was engaged for 18 months; Danielle, who was 19 when he married her in 1944 aged 28; and Anne Pingeot, who was 20 when he began a love affair with her at the age of 47 and who bore him a daughter, Mazarine. Philip Short shows that Mitterrand’s love for Anne also fired his conversion to socialism, though he never left the long-suffering Danielle. To be a Machiavelli with a secret passion was perhaps the supreme ambiguity.