Comment: Tuesday Book: His time was short, his vision long

BONAR LAW BY R J Q ADAMS, JOHN MURRAY, pounds 25

AT BONAR Law's funeral in 1923, Asquith cuttingly remarked: "We are burying the unknown Prime Minister." Law was Prime Minister for just seven months - the shortest tenure of any modern holder of the office. Yet he was not Prime Minister by accident. He had been a highly successful leader of the Tory party for 10 years and Deputy Prime Minister for five; and it was not political defeat which cut him short, but cancer. He was a leading figure in the tumultuous decade before, during, and after The Great War, who played the central role in pulling down the last two Liberal prime ministers before taking the office - reluctantly - himself. For all that he held the job for only seven months, he was a considerably more substantial figure than John Major, who held it for seven years.

It is a major gap that there has been no new biography of Law since Robert Blake's in 1956, especially in view of the quantity of source material now available. There can be no period of political history so rich in written evidence. It was a period of huge party-splitting controversies conducted by a small class who mixed across party lines and wrote voluminously to one another. We know almost too much about this cast of characters, and their movements and machinations.

The story of the replacement of Asquith by Lloyd George in December 1916 has been told so often by biographers that one more turn round the course inevitably has a sense of deja vu. Yet it remains endlessly absorbing, as do the showdown over the peers' veto, the posturing brinkmanship over Ulster, the downfall of Lloyd George and the other dramas of these years. Professor Adams rehearses them all authoritatively and well.

What is striking is how topical these issues still are. We are still arguing about how to complete the reform of the House of Lords, begun in 1911. We are still trying to satisfy the irreconcilable loyalties of Unionists and nationalists in the north of Ireland. We are still trying to avoid unwinnable wars in the Balkans and the Middle East. Nothing could be more relevant today than Bonar Law's warning, when the Lloyd George government was threatening war against Turkey in October 1922, that, "We cannot act as the policeman of the world".

Law was a curiously modern figure in another way. He was the first of a new meritocratic breed of Tory leader. A Glaswegian-Canadian iron merchant who had not been to university and boasted no cultural pretensions beyond a love of bridge, he represented a startling contrast with his aristocratic predecessors, Salisbury and Balfour. He drew the snobbish condescension of Balliol men such as Asquith, who called him a "gilded tradesman". But he set the tone for his two successors, Baldwin and Neville Chamberlain. Churchill reclaimed the party for the toffs, followed by Eden, Macmillan and Home. But Ted Heath suffered exactly the same sort of snobbery in opening the way for Mrs Thatcher, Major and William Hague.

Fascinated as we have become by Tory leadership elections, the story of Law's emergence as compromise candidate between Austen Chamberlain and Walter Long in 1911 intriguingly anticipates the contests of 1975, 1990 and 1997. The Tories always choose the unlikeliest candidate. But whether - as Adams' jacket suggests - the story of Law's success in leading the party out of the wilderness holds out much encouragement for Hague, is doubtful. The Liberals' massive majority of 1906 had already been eroded by 1910, and Law faced a government uncomfortably dependent on the Irish, losing momentum well before 1914. But for the First World War, Law would surely have become Prime Minister in 1915. It is difficult to say the same of Hague in 2001.

The only disappointment of this book is that it tells so little about Law's early life - the most interesting part of most biographies. Born in Canada but brought up by relatives in Glasgow from the age of seven (or possibly 12), he joined his adoptive family's firm at 16, became a successful trader in the Glasgow Iron Ring, joined a parliamentary debating society, married and fathered six children, and was elected for a Glasgow seat in 1900 at the age of 42.

All this takes fewer than 20 pages. Thereafter, the private man largely disappears, except for assurances that he was a devoted husband (widowed at 51) and father, devastated by the loss of two sons in the war. Perhaps there is nothing more to say.

Law was a notoriously unsociable workaholic. Yet he is an oddly endearing character, a wonderfully gloomy Eeyore, the perfect foil to Lloyd George's bouncy Tigger, much as Attlee was to Churchill in the next war. One would love to know more of the chemistry of this relationship. That apart, however, Professor Adams's book is a model of lucid and authoritative political biography.

The reviewer's life of Edward Heath was published in 1993; he is writing a biography of Margaret Thatcher