THE DOWNFALL of Winston Churchill in the Dardanelles disaster of 1915 reminded his friends of the downfall of another enfant terrible, of his father, Lord Randolph. Once again people muttered: we told you so. Father and son could talk and act like angels. They had eloquence, audacity, imagination, and they were like Lucifer, both of them, destroyed by their impatience, ambition, egotism. Their falls, it was noted, were "Miltonic." In resigning from Salisbury's cabinet in 1886, Lord Randolph staked his career on a single pointless throw. Winston, too, seemed to believe, against all reason, in his star, and like a star he fell from the heavens, from Asquith's inner cabinet, to the mud of a company comme ordander's outpost in the trenches of 1915.

Then of course the resemblance between father and son proved altogether an illusion. Winston was no Lucifer, it was clear, as he scrambled back up the safety rope he had carefully prepared, dusting his top hat and puckishly relighting his cigar. Tableau! He was Buster Keaton or Houdini or Superman. With one bound the doomed hero was free. With one more bound he had fallen backwards off the high wire.

His career, the cliffhanger of the century, has been the making of numerous admirable books. There's the majestic official biography now in progress, that legion of volumes begun by his son Randolph, continued with equal gusto and even more skill by Martin Gilbert. There's Robert Rhodes James' brilliant literary etching, A Study in Failure. There's an excellent one-volume biography by Henry Pelling. And of course no biographer ever wrote more confidently about the greatness of his theme than Churchill about himself. How can a new biography, dependent on such well-known sources, look anything but pale by comparison? Inevitably this life of Churchill by Ted Morgan, covering his career to 1915, will disappoint Churchill's fans. It is a competent summary, no more, of the episodes leading to Churchill's first downfall.

True, Ted Morgan gives us a few insights of his own. He tells us, for example, that Mrs. Everest (Churchill's nanny, immortalized in My Early Life) "Toilet-trained him . . . she held his penis while he urinated, and washed it for him afterwards." Sometimes, too, Morgan doggedly seizes the wrong end of the stick. He claims that "to Kitchener, who did everything by the book, Churchill was dangerously free-wheeling." In fact Kitchener, a fellow victim of egomania, disdained the idea there was a book to go by. He shared Churchill's genius for fatal shortcuts. But mercifully Morgan has little to say of his own. His worst habit is that of muddying quotations by paraphrases. It is a man's own voice, above all, that should vibrate through his biography, and what a voice there was here: like a roll of drums. Still, I read more or less cheerfully to the end. No one could write a dull book about how Churchill was destroyed by a war. The story, like the man, is irrepressible.

It was war that first catapulated the young Winston to fame--at his third try. He had first fought in India and in the Sudan. Then in 1899 his impudent escape from a Boer prisoner-of-war camp in Pretoria, and his bumptious writings as a soldier-reporter, struck the right note with the British public exasperated by the humiliations of the Boer War. He made s10,000, mainly out of writing and lecturing on his escape, and used the money to dive headfirst into parliament, taking Oldham for the Tories in the Khaki Election of 1900. A change of parties (to the Liberals, the first of three changes of party) was followed by a masterly biography of his father.

In this he not only put a golden glow on his father's memory, but ingeniously explained away his own desertion of his father's old party. For it was implicit in his own account that Lord Randolph was a liberal imperialist manqu,e, a man betrayed by his incurable loyalty to the Tories. (Winston understandably played down the other source of his father's tragedy: incurable syphilis.) At 33, even younger than Lord Randolph, he joined the cabinet, and introduced many social reforms as Asquith's president of the board of trade. He had, as he had promised years before, "beaten his sword into an iron despatch box," but it was already clear the metal was flawed. He was a genius, but a genius, as Asquith remarked, "with no judgment." (Years later Attlee put it more crudely: he was "50 percent genius, 50 percent bloody fool.")

In the next few years Churchill's future was the central enigma of British politics. At times he still seemed to lean too heavily on his father's example. In 1909 he lobbied against the British naval rearmament program in a conscious echo of his father's quixotic resignation over the army estimates of 1886. But soon young Winston (unlike Hamlet) learned how to get the right advice from his father's ghost. The chief lesson of Randolph's fall was that he had prepared no safety rope--or what Winston called ''The Reentry Card." Winston's rope was held by Lloyd George, whom he helped save from disaster in the Marconi scandal. Fellow climbers, and buccaneers, were Birkenhead and Beaverbrook. (And, as we have learnt from Mary Soames' moving biography, Clementine, Winston was better served by his wife's counsels than was Randolph by the frivolous Jennie.) In the Home Rule crisis of 1914, Winston neatly inverted his father's Irish policy. "Ulster will fight, Ulster will be right" was reinterpreted to mean, Ulster will bury the hatchet. And, through overruled by Asquith, he threatened to beat his father's old Orange friends on the head with the navy.

By the outbreak of the Great War, Churchill mounted the heaviest guns, apart from Lloyd George's, in Asquith's cabinet. As first lord of the admiralty, under the spell of Admiral Fisher's erratic genius, he reversed his own ideas on naval rearmament. He built bigger, faster, better-armed dreadnoughts than the Kaiser. He encouraged (and, at great personal risk, piloted) the newest models of aeroplane. He helped develop brilliant innovations, which were to culminate in the tank. And at the same time he made one colossal error of judgment. This was to rescue Fisher from retirement and install him as first sea lord. Fisher parodied his own faults--especially his mercurial temperament and his habit of rubbing people up the wrong way. It was not long before war broke out between first lord and first sea lord. Fisher's own resignation in May 1915, and the developing nightmare of the Dardanelles, was designed by Fisher to precipitate Churchill's downfall.

He survived the crash by an inspired mixture of courage and showmanship. He rejoined the army and fought gallantly as a humble major in the trenches. By 1917 he had bounced back as Lloyd George's minister of munitions. He had lost many friends and most of his reputation, but he had kept intact what was most important. Against all reason, he believed he had an appointment with destiny. And three downfalls later, in May 1940, as all the world knows, the call came.