The Pain and the Privilege, by Ffion Hague

History used to be about chaps. Now it is about the women behind the chaps. From Henry VIII's wives and Louis XIV's mistresses to Churchill's mother and Wordsworth's sister, the shops are bursting with books predominantly by women, illuminating the lives of women who in their time were overshadowed by husbands, brothers, sons and lovers. There is clearly a feminist agenda here; but it is also an excellent way of throwing new light on the great men whose lives have been done to death by conventional biographies.

The downside is that someone like David Lloyd George is remembered more for his private life than his public achievements. The Liberal statesman who won the Great War, laid the foundations of the welfare state and gave independence to Ireland is reduced to nothing more than a randy womaniser. Ever since AJP Taylor published the diaries and letters of Lloyd George's mistress, Frances Stevenson, the story of his double life has been told and re-told in ever greater detail. I have added my mite to this reputation. But the emphasis is wrong. Lloyd George always put politics first, and his women were ruthlessly subordinated to that priority.

Ffion Hague's book extends the canvas by considering all the women in Lloyd George's life. Perhaps the most important were the earliest – his mother Betsy and sister Polly, who instilled in the young David the belief that it was his entitlement to be loved, cosseted and spoiled by women. Unfortunately, they remain fairly shadowy figures. Hague has more to go on with his first girlfriends – he started young – and then his determined courtship of Maggie Owen against the opposition of both families, which he documented with extraordinary frankness.

Little of this is strictly new, but she prints it for the first time in a mainstream biography. The same applies to LG's affairs with Elizabeth Davies ("Mrs Tim") and Julia Henry – the wives of fellow Liberal MPs – in the 1900s, and his alleged fling with another woman, Kitty Edwards, who claimed unsuccessfully that he was the father of her child a few years earlier. If there were others she has not uncovered them; but the known facts are thoroughly rehearsed in a fluent, balanced and broadly sympathetic narrative, as is the long and complicated relationship with Frances Stevenson which dominates the last two-thirds of the book.

Where Hague does have both a new perspective and new material is in her treatment of Margaret Lloyd George, who has been seen too much through the eyes of Frances. Writing as a political wife herself – and a Welsh-speaking one at that – she brings a sensitive understanding to Margaret's determination to bring up her family in North Wales, even though this left her husband dangerously alone in the capital.

She also understands the world in which the susceptible Lloyd George was stalked by ambitious hostesses. Above all, she reclaims Margaret as a significant political figure – not at all the homely body portrayed by earlier writers, but a formidable local politician in Caernarvonshire who effectively held Lloyd George's constituency for him for 50 years and acted as a model PM's wife when he moved into Downing Street. Controversially perhaps, she suggests that Margaret did not realise the seriousness of LG's relationship with Frances until after the war.

Thereafter Hague follows the complex ramifications of the triangular affair with remarkable empathy for both women. She tends to the view that Frances's daughter, born in 1929, was not Lloyd George's but Thomas Tweed's, even though her calculation of dates ignores evidence that the baby was premature (which actually supports her case). True to her title, she also gives generous space to LG's daughters, Olwen and Megan.

All these women in their different ways helped to promote and protect Lloyd George's extraordinary career. In private he was monumentally selfish; in mitigation, he devoted his life tirelessly to great democratic causes. But amazingly little of this intrudes here. Perhaps political biography with the politics left out is an appropriate metaphor for the Age of Blair.

John Campbell's 'If Love Were All: the story of Frances Stevenson and David Lloyd George' is published by Vintage