In particular, it is salutary to be reminded of the catastrophic sigh of relief - three quarters of a century ago - with which the British political class shifted its attention from an insoluble tangle over Northern Ireland to a distant quarrel in the Balkans, about which all parties could feel a glow of righteous indignation. It is chilling, too, to be reminded of the confidence that Bonar Law shared with his contemporaries, that the war on which this country had so readily embarked could be contained.
Bonar Law, however, deserves to be remembered for other reasons. As premier, he may have been a mere "sometime" - his 211-day tenure the shortest in recent history. But as a key figure in British politics, he had a profound influence during tumultuous years. He was also a man who aroused strong feelings. Few statesmen have inspired a greater respect and liking, and few more anger and frustration.
He was also one of the most unlikely leaders. Tory politicians in his day were supposed to be roast-beef-eating John-Bull aristocrats. Law could scarcely have been further from this stereotype: the American, log-cabin- to-White House myth comes closer. He was Britain's only Canadian premier. Born in New Brunswick the son of an Ulster-born Presbyterian minister, Law spent his earliest years in a homestead that was little more than a shack.
What lifted him from this unpromising background was the early death of his mother and his adoption by remote Scottish cousins who paid for his education at Glasgow High School, and employed him in the family merchant bank. Though he left school at 16, he attended evening lectures at Glasgow University. As a boy, Abraham Lincoln learnt every verse of Psalm 119 by heart: it was Law's boast that he had read Gibbon's Decline and Fall of the Roman Empire three times before he was old enough to vote.
The Glaswegian bourgeoisie were then (and probably still are) divided into three groups: the Strivers, who travelled to work on the seven o'clock commuter train, the Drivers who did not leave home until after their morning tea, and the Thrivers who rolled into the office after 10. Bonar Law was a lifelong Striver, hardworking, teetotal and regular in his habits. He also "took politics with his porridge" - both in the aspirantly puritanical household of which he was a member, and in the rough-and-tumble of the Glasgow Parliamentary Debating Association, where he was able to develop rhetorical skills.
There was no meteoric rise. In banking, and then as partner in a metal trading firm, he was solidly rather than spectacularly successful. In 1891 he married the daughter of a wealthy manufacturer. His parliamentary career did not begin until 1900, at the age of 42. Although his biographer claims that he made an early impression as a Tariff Reformer (the early 20th-century equivalent of a Eurosceptic), his political life was nearly terminated by a series of disasters. In the 1906 Liberal landslide, he lost his seat to a Labour candidate; three years later, his wife died, leaving him with six children between the ages of four and 15. Thereafter, it was said that he "habitually bore an air of sadness".
He was 51 and out of Parliament: prospects looked grim. In fact, his career as a front-rank politician was about to take off. Despite tragedy and setback, he returned to the House in May 1910. There was now a reckless edge: in the second election of 1910, he gave up a seat to act as standard- bearer for the Tariff Reformers in a constituency in Manchester, home of free trade. He did not win, but - having gained the aura of a Tory hero - was quickly found a seat elsewhere. A sign of his stardom was his involvement in the founding in 1911 of the super-select Other Club, with Winston Churchill and F E Smith. Meanwhile, the young Max Aitken, later Lord Beaverbrook - also a native of New Brunswick, and of Ulster Calvinist stock and newly docked in London - had made his way to Law's dinner table, offering his services as financier, publicist, acolyte and companion. The two became firm friends, to mutual benefit. At the end of 1911, egged on by Aitken, Law allowed his name to go forward for the Tory leadership as a compromise candidate. The two front-runners, Austin Chamberlain and Walter Long, feared a stalemate. Both agreed to stand down and - to his own astonishment and alarm - Law won without a fight.
Few choices could have seemed odder. Some Tory MPs felt uneasy. One commented that the party was "behaving like a gentleman conscious he has married beneath him", while the inimitable Margot Asquith observed to St Loe Strachey that politically Law was "the most sophistical untrue unsound gerry-built quick clever affectionate vulgarian I've ever seen". As usual, she missed the point. What Law offered was a set of honest instincts that fitted precisely the dominant prejudices of his party at the time.
On many matters, he was a reactionary in the sense that he had no policy except to react negatively to the initiatives of the other side. On women's suffrage, for example, he deemed it to be beneath the dignity of the Conservative Party to have any view at all. Ireland, however, was the exception. Law once told Austin Chamberlain that until the First World War, "he cared intensely for only two things: Tariff Reform and Ulster; all the rest were only part of the game." On Ulster, his father's native land, he argued, with a consistent, blocking fervour, that no Home Rule settlement was permissible unless an election was held first. To Liberals, he came across as a dangerous bigot; to his followers, as indomitable. His style was bantam-weight: neat, incisive, quickly back on his feet, and - in the words of a grudging admirer - with "the great virtue of being very unacceptable to his opponents in the House of Commons".
He also had the notable virtue - or political skill, depending on your degree of cynicism - of not arousing jealousy when the competition got intense. He gave an appearance of modesty, diffidence, even selflessness, which may or may not have belied the reality. The 1911 leadership contest provides one illustration of this aspect to his personality. The War provides others. Thus, after a crisis in 1916 produced the first Coalition, Law accepted without complaint the Colonial Secretaryship, a post a more vainglorious leader of his party would have found insultingly minor. A few months later, dissatisfaction with the conduct of the war caused a new paralysis, and the King asked Law to form a Government. Another kind of leader would have gone for it: Law remained listless, and the opportunity (if such it was) passed. "I was not at all sure," he explained, "that I was equal to such a position at such a time."
His decision was no doubt the right one. At any rate, it enabled him - as Leader of the House, Chancellor of the Exchequer and deputy Prime Minister - to become the second most important member of the new Lloyd George Government.
These were glorious times for Bonar Law, as the War was brought to a triumphant conclusion. They were his zenith. But they were terrible times as well. Within five months in 1917, Law lost two of his sons, one barely out of school. His eldest, a pilot, was shot down in France during the battle of Passchendaele. The author gives a heartrending account of how, accompanied by Beaverbrook, Bonar Law crossed the Channel and asked to see an aircraft of the type his son had flown. He then lowered himself into the cockpit of a small, battle-scarred plane and sat silent and alone for two hours. After each personal disaster, he appeared at first inconsolable. Then he simply carried on. Only when the war ended did he let his feelings show. Lloyd George wrote: "He just reads and smokes and works." During the post-Armistice celebrations, he wept as he told a friend, "This is what the victory means to me - time for a moment to mourn my dead."
Eventually the toll proved too great. "Bonar Law ought to take a drink," Lloyd George remarked. "...Failing drink, the only remedy for Bonar is a wife." He took neither, and in March 1921 physical exhaustion caused him to resign all his offices, though he remained an MP. It should have been the end: but he could not keep himself from the fray, particularly in the search for a lasting settlement over Ulster. When in the following year the Tories decided to pull the rug from under Lloyd George, Bonar Law seemed the obvious successor: a sombre, unflappable, politically sound, safe pair of hands. Law was reluctant, but he allowed his will to be broken by the flattery of younger men, with agenda of their own.
It was a dreadful error. There was an initial success: Law led his party into a landmark general election that signalled the recovery of the Conservatives as an independent force, and the permanent demise of the Liberals. Then cancer of the throat took hold. The new premier attended the wedding of the Duke of York and Elizabeth Bowes-Lyon in April 1923. The following month - having lost the ability to speak above a hoarse whisper - Law resigned. His last political act was to steer the succession away from Curzon, whom he and many others expected to take over, and towards Stanley Baldwin. He died in October. The Labour leader, Ramsay MacDonald, observed that he wrung from the opposition "a strange mysterious sympathy".
What, if anything, did he achieve? Adams claims for him the recovery of the Conservative Party, and it is certainly arguable that during his decade as leader he helped to save it from its worst contradictions, and to ensure that it was the Liberals who were destroyed by the rise of Labour. As much as any other British politician, Law can also be credited with the retention of protestant Northern Ireland in the United Kingdom. Yet it was in the nature of his paradoxical style - lonely, yet interwoven with the fabric of his team - that the consequences of his actions are hard to unravel. All politicians who want to be appreciated by posterity should keep diaries: Law left scant papers, which makes his contribution the harder to unweave. It also means that this book is almost exclusively a political study. Adams does his best on the Law family, but there is really very little to go on.
Nevertheless, the evidence gleaned from a range of sources has enabled the author to write a fascinating as well as definitive work, and to provide a convincing portrait of a substantial character. "All great men are humbugs," Bonar Law once remarked to Clemenceau, no doubt thinking of some of his own brash and flash contemporaries. Bonar Law was a Conservative in the old-fashioned sense, without an ounce of ideology. He defended, and did not create. He was not great. But, as Professor Adams shows, he was not a humbug either.