IT WAS 50 YEARS AGO that Winston Churchill commenced his lonely crusade to awaken England and the world to the menace of Adolf Hitler. The story of that voice crying in the wilderness, though fit to stand with the legends of English-speaking history, is all but unknown to later generations.

But help is on the way. "The Wilderness Years" starts this evening on PBS' Masterpiece Theatre. It may be another grim omen of post-literacy that the instrument of the Churchill revival is to be television. But better that than ignorance. And in case the television series whets bolder appetites, we have this short account of those years by Churchill's official biographer, Martin Gilbert of Oxford.

Gilbert took over the work left only barely begun at his untimely death by Randolph Churchill. He has expanded it to monumental length, so formidably detailed that one needs a compass--or a strand of Ariadne's hair --to negotiate the trackless pages.

Fortunately the prospect of a bull market for Churchilliana has prompted Gilbert to distill a more compendious account from the huge fifth volume. It is an excellent distillation. Gilbert, co-author of The Appeasers, has been on this story for 20 years and knows it inside out. This is his notion of its essence, with new information and thematic refinements that did not appear in The Appeasers.

Winston Churchill, although he was by 1933 the senior figure in British public life--he was nearly 60--had held his last Cabinet post (chancellor of the exchequer under Stanley Baldwin) before the turn of the decade.

Great though his prestige was, wide though his circle of friends, he was too independent to fit orthodox political niches. Hidebound Tories held it against him that he had bolted the Conservative Party in 1904 and followed the Liberals Asquith and Lloyd George. Labour regarded him (falsely) as a social reactionary. High- minded anti-imperialists of both parties found his views on Indian independence retrograde. (He still believed in Britain's civilizing mission there, where Moslems and Hindus were at odds and millions of "untouchables" pariahs.)

Thus on many grounds Churchill's political judgment was suspect--even his clearmindedness on the menace of Hitler. But Churchill had history in his bones. He understood, as if instinctively, that air power had compromised Britain's long immunity to attack. His view of Hitler was unclouded by the sappy pro-Germanism of the insular Tories, who hoped that at worst the Nazis and Bolshies might devour one another and leave others alone. Finally, unlike the pacifists of the left, he saw disarmament as a deulusion so long as the Nazis were bellowing for a forced revision of the Versailles Treaty. He correctly insisted that treaty revision must proceed from strength, not weakness.

The rest of the story is familiar, or used to be--how Churchill begged, pleaded, cajoled while the Baldwin government let military parity slip away. How pleading turned to anger as the Chamberlain government, military parity lost, turned to appeasement in the hope of avoiding war.

Always, he spoke with inimitable eloquence. In November 1936, he said the government "in strange paradox (is) decided only to be undecided, resolved to be irresolute, adamant for drift, solid for fluidity, all power to be impotent."

Two years later, after the infamous Munich agreement had consigned democratic Czechoslovakia to piecemeal dissection, he characterized Hitler's tactics this way: "One pound was demanded at the pistol's point. When it was given, two pounds were demanded at the pistol's point. Finally, the dictator consented to take one pound, 17 shillings and sixpence and the rest in promises of goodwill for the future."

Time and the documents have confirmed Churchill's worst suspicions of the Baldwin-Chamberlain governments' delinquencies. Gilbert is not gentle in driving the point home. What he adds here is much fresh information on the sources of Churchill's prophetic speeches. The prophet was being leaked to in great volume by sub-cabinet officials who shared his alarm--people like Sir Desmond Morton and Torr Anderson of the Royal Air Force, as well as the valiant Ralph Wigram of the Foreign Office. (So much for those who regard leaks as, invariably, a political evil!)

Those who can't get their fill of Churchill lore will also value Mary Soames' collection of photographs from the private family collection. Some are familiar; most are new. The accompanying text is pleasant and informative.

Examining this rich album of pictures of the greatest English-speaking statesman since Elizabeth I, I was struck for the first time by a Churchill eccentricity. Churchill was a great fancier of hats. He must have owned hundreds, from pith helmets to sombreros, all shading that immortal cherub's face.

The hat has gone into eclipse. But the story of the man in the hats cannot be told too often. It is good to know that millions are about to learn it--or at least one of its celebrated chapters--for the first time. With all due praise to the excellence of British television drama, these novices will know the story better if they also read these two timely books.