(SECTION) CENE: A country house in Hampshire during a February weekend in 1912.

"I was sitting with her in the dining room on Sunday morning--the others being out in the garden or walking- and we were talking and laughing on just our old accustomed terms. Suddenly, in a single instant, without premonition on my part or any challenge on hers, the scales dropped from my eyes; the familiar features and smile and gestures and words assumed an absolutely new perspective; what had been completely hidden from me was in a flash half-revealed, and I dimly felt, hardly knowing, not at all understanding it, that I had come to a turning point in my life."

Herbert Henry Asquith, almost 60 and prime minister of England for the past four years, has fallen in love. His object: Venetia Stanley, who comes from an eminent Liberal family, is just 25, the same age as Asquith's daughter Violet and her close friend.

Thus began an extraordinary relationship, charted in the 560 surviving letters (half printed in this volume) which editors Michael and Eleanor Brock call "the most remarkable self-revelation ever given by a British prime minister."

Asquith was at the peak of his career. From genteel and emotionally deprived beginnings he had risen to eminence at the bar, then to leadership of a Liberal government which laid the foundations of Britain's welfare state, modernized the army and navy, subdued the House of Lords, and was running a grave risk of civil war by offering Home Rule to Ireland.

Through all these crises, however, Asquith gave the impression of amiable self-control. He enjoyed golf and bridge with his well-to-do cronies. He liked the pleasures of the table and the company of smart, lively women. (His aristocratic foreign secretary, Sir Edward Grey, talked about "old Squiffy and his little bourgeois legs" trotting into society.) But he was not a snob, nor was he a womanizer like his colleague David Lloyd George. His second wife, the tart, nervy and extravagant Margot, openly tolerated the avuncular pleasantries with which he cultivated "his little harem"; and in a scarcely believable letter published in this volume (written, astonishingly, to the man Venetia Stanley was about to marry) she even claimed that "every night . . . he shows me all his letters and all Venetia's and tells me every secret."

Venetia was also outwardly cool, an early flapper to judge from Asquith's gentle reproofs for her flippant language and the lack of any serious pause in her round of pleasures; and yet he took her seriously enough to pass on every nugget of political chitchat. She seems to have been the kind of woman that H.G. Wells described in his Edwardian novels--dark-eyed, with aquiline good looks and a masculine turn of mind. One of her contemporaries described her as "a splendid, virginal, comradely creature, reserving herself for we knew not what use of her fine brain and hidden heart."

The words were apt. Though Venetia was flattered by "The Prime's" romantic ardor--what young woman could resist a correspondent who could break off a love letter with "darling, I must stop now as I have to go and see the King"?--she does not seem to have reciprocated it with any warmth. She was content to be one of those intimate companions that lonely and over-burdened men seek out with their confidences.

And the confidences do roll out day by day, sometimes twice a day and more. Asquith wrote easily, and there are some agreeable anecdotes. Here is Henry James at dinner building a tower of epigrams "and as often as not leaving the building half-finished with the scaffolding still around it"; or Rupert Brooke, leaving for the war, "quite convinced that he will not return alive"; or Churchill, admired for his talents and distrusted for his character. But all these diary-like phrases are nothing to the spate of infatuated prose, which gathers pace as the storm of war breaks over Europe. "I came away a new man," Asquith writes on October 22, 1914, "thanks to your life-giving and unfailing power of restarting run-down springs, and refilling exhausted reservoirs, and regenerating the whole being and life of a man."

"My beloved," he writes two weeks later. "No one can say that we kept our lamps unlit, or allowed them to grow dim and flicker out. . . . If I were to die tonight, your name would be graven on my heart, and the thought and vision of you would be my last and dearest memory."

And then, early in March 1915, when Venetia was covertly planning to marry his colleague and close friend Edwin Montagu, Asquith declaims so passionately that his subsequent humiliation was to be all the worse. "My love for you has grown day by day and month by month and (now) year by year: till it absorbs and inspires all my life. I could not if I would, and I would not if I could, arrest its flow, or limit its extent, or lower by a single degree its intensity. . . . It has rescued me (little as anyone but you knows it) from sterility, impotence, despair. It enables me in the daily stress of almost intolerable burdens and anxieties to see visions and dream dreams."

It was also an attachment so strong that it led Asquith into staggering indiscretions. Any one of the letters he sent to Venetia in the first six months of the war would have put a lesser politician in the Tower and an army officer in front of a firing squad. They contain precise details of troop movements, of the dates of coming offensives, the state of munition supplies, naval losses, arguments in the high command, quarrels with the French. Asquith sends her reports from Sir John French, commanding the British Expeditionary Force in France, confidential comments from his war minister, Lord Kitchener, and secrets unknown to other members of his government. "All this rather kept back from the Cabinet," he writes insouciantly, telling her that the Dardanelles attack is being delayed while the Allies settle "how cheaply we can purchase the immediate intervention of that most voracious, slippery, and perfidious power--Italy." He is so careless that he even tosses a deciphered dispatch out of the car window while he is taking her on her regular Friday afternoon drive.

These letters, of course, have already been used by biographers (especially in biographies of Asquith and Churchill) and their fuller publication does not reveal any particular surprises about the origins of World War I; nor do they add much beyond a succession of fascinating details about the politics and fighting during its first year. What does emerge is the scale and the irresponsibility of Asquith's gossip. To be fair to him, the standard of security at society dining tables (and in pillow talk) was not much better in 1914 than it was before Waterloo, a century earlier. Sir John French was writing to Winifred Bennet from the Western Front with no more discretion than Asquith wrote from Downing Street to Venetia in her war-nurse's quarters in London. But Asquith showed scarcely a verbal qualm as he sent one state secret after another through the public penny post.

It is hard to guess at the motives which drove him-- harder, perhaps, because Venetia's letters are lost and she was, in any case, emotionally arid and psychologically opaque. But they were clearly more powerful than the conventional vanity with which an aging man seeks to impress his youthful "inamorata," stronger even than the compulsions of a war-leader who needs someone to share his traumatic knowledge as urgently as the neurotic seeks the comfort of an analyst's couch. For there is a desperate and obsessional tone echoing all through these letters--a sense of hopeless dependence that might possibly have been shaped in a fatherless mid-Victorian childhood.

The whole affair is an intriguing example of a private drama played out on a public stage. Asquith had welcomed this sudden infatuation as the Irish crisis broke as the best luck of his life, and the break with Venetia came at another decisive moment of his career. He was already in trouble as the Dardanelles campaign proved a disaster and the shortage of shells in France gave his critics a chance to force him into a coalition. On May 12, 1915, the morning after Venetia's midnight message told him that she proposed to marry Montagu, he wrote her three lines.

"As you know well, this breaks my heart.

I couldn't bear to come and see you.

I can only pray to god to bless you--and help me."

Three days later he had taken the Tories into his government. Nine months later they pushed him out of office and he spent the rest of his political career in disillusioned futility.