ANTHONY EDEN By Robert Rhodes James McGraw-Hill. 665 pp. $22.95

ANTHONY EDEN looked like a prime minister, as Ronald Reagan looks like a president -- slim, elegant, with a clipped mustache and a gift for a rallying followers. As Neville Chamberlain's foreign secretary, he was the preux chevalier of the House of Commons -- "the one fresh figure of the first magnitude," wrote Winston Churchill, "arising out of a generation which was ravaged by the war."

His background was flawless. Educated at Eton and Christ Church, Oxford -- where he took a first in oriental languages -- he was a genuine hero of the Great War, a decorated brigade major at the age of 21. After the Hoare-Laval plot to sell out Ethiopia -- "No more coals to Newcastle and no more Hoares to Paris!" said King George V -- Eden became Britain's youngest foreign secretary since the 1770s. His policy was supportive of collective security and the League of Nations. But Chamberlain disliked the League and rather favored the dictators. Most of his executive experience had been in Birmingham. As Churchill put it, he saw foreign affairs "through the wrong end of a municipal drainpipe."

Courting Mussolini, Chamberlain decided to recognize Il Duce's conquest of Ethiopia. Eden, sandbagged, resigned and became the champion of dissident Tory MPs fighting appeasement. Churchill was a lonely figure then. At one point he had four supporters in Parliament, one of them his son-in-law. Less than a year before World War II broke out, as Robert Rhodes James has written elsewhere, "three distinct groups were formed, headed by Eden, Churchill, and Amery, and of these the first was by far the largest."

And yet . . .

Eden always nailed his colors to the mast, but not always to the same mast. He craved popularity and was awed by power. Had he been a man of greater scruples, he would have quit the cabinet long before. The prime minister had repeatedly insulted him in the presence of others, had consulted foreign governments without even informing the Foreign Office and, once, had taken the Italian ambassador's side against his own foreign secretary. Earlier in the decade Eden had been a tribune of appeasement, supporting German rearmament, telling the House that meeting Nazi demands was certain "to secure for Europe that period of appeasement which is needed." If appeased, he argued, Hitler's anger wouuld vanish, together with his fear of encirclement; the Nazis, freed from insecurity, would become stable neighbors in a Europe free of rancor. Parliament gave him a standing ovation. Churchill remained seated.

At the time of Eden's appointment, Winston had written his wife that it "does not inspire me with confidence. I expect the greatness of his office will find him out," adding, two weeks later, "I think you will now see what a light-weight Eden is." During the Munich crisis of 1938, Eden refused to sign a telegram begging the prime minister not to betray the Czechs "on the grounds," according to Harold Nicolson's diary, "that it would be interpreted as a vendetta against Chamberlain," and as late as July 18, 1939, Nicolson noted, "Anthony does not wish to defy the Tory party and is in fact missing every boat with exquisite elegance."

Nevertheless in 1942 Churchill, having succeeded Chamberlain and become leader of a nation in arms, wrote Buckingham Palace that in the even of his death he hoped the king would "entrust the formation of a new Government to Mr. Anthony Eden," whom Winston had restored to the Foreign Office and "who, I am sure, will be found capable of conducting Your Majesty's affairs with the resolution, experience and capacity which these grievous times require."

What had happened? It would be uncharitable to suggest that Eden had avoided Churchill when Winston was a pariah and now warmed to him as his popularity soared. Like most Britons, the once and future foreign secretary, remembering his misery in the trenches, had hoped desperately that appeasement would succeed. Churchill had done his utmost to sabotage that policy, knowing it would mean war in the end, with Nazi Germany favored to win, and Eden had scorned him.

However, once the light had dawned -- once Parliament had wrenched power from Chamberlain and turned to Churchill -- Eden had returned to the Foreign Office and become the ablest member of the Churchillian cabinet. At the same time, it is possible to read too much into Winston's advice to the king. He knew Eden as a superb subordinate. He was not so sure about his qualifications as the nation's leader. He had flickers of doubt about the younger man's judgment. Although he had anointed Eden as his heir, he worried about him, and that was one reason he delayed his retirement until 1955, when he was 80. Eden moved into No. 10 Downing Street then. The Suez crisis, and his fall, came the following year.

Rhodes James is among England's most brilliant historians and himself a Member of Parliament. His biographies of Lord Randolph Churchill, Lord Rosebery and Victotia's consort Albert established him as the peer of A.J.P. Taylor and Hugh Trevor-Roper, and his Gallipoli is regarded as the definitive account of that tragic campaign. Perhaps the most perceptive, and certainly the most controversial of his works, is Churchill: A Study in Failure, 1900-1939. Although the reasoning is sometimes jesuitical, with material subordinated to his daring argument, A Study in Failure was recognized as a welcome antidote to panegyrics which, by enshrining Churchill, presented him as bloodless and hardly mortal.

As the chronicler of Eden's life, he confronted a problem familiar to all authorized biographers. He undertook it at the request of the late Clarissa, Countess of Avon, Eden's second wife and widow. Having discussed her husband's career at length with Lady Avon, I can testify to her dedication to his memory and her resentment of any suggestion that he was a statesman without imperfection. Rhodes James was entrusted with exclusive access to those Eden papers not already catagued in the University of Birmingham Library. Lady Avon would be pleased with the resulting volume. Oddly, the book is not annotated. The scholarly apparatus is confined to a select bibliography, citing fewer than 30 titles.

Rhodes James devotes 157 pages, 25 percent of his text, to Suez. It is a riveting yet unbiased account. His generosity to Eisenhower is surprising and perhaps not wholly deserved; Macmillan is seen as vacillating; John Foster Dulles is rightly indicted for his irresponsibility, first creating a problem and then condemning the British for their attempt to solve it.

The fact remains that the Anglo-Franco-Israeli plan for an invasion of Egypt carried within it the seeds of its own destruction. In a world dominated by the Soviet Union and the United States, Victorian gunboat diplomacy was doomed before the troops embarked for Suez. And Eden, whose health had always been frail, could not bear the strain. With the issue unresolved his doctors recommended a rest in Jamaica. It was sound medical advice but wretched politics. In the Manchester Guardian Randolph Churchill wrote that Hitler had refused to withdraw his Sixth Army from Stalingrad, but "even Hitler did not winter in Jamaica."

And so misfortune and bad judgment destroyed the most promising statesman of his generation. All his achievements, his valiant services to Churchill, were forgotten. Rhodes James reminds us of them, and the result is an enthralling, persuasive, invaluable account to be read, cherished, and given its proud place on every reference shelf. The British edition carries on its jacket the quotation: "The morning was golden; the noon was bronze; and the evening lead. But all were solid, and each was polished till it shone after its fashion." Actually those lines were written by Churchill, and he was describing Lord Curzon: aristocratic, fastidious, thwarted, flawed. But they would serve well as Eden's epitaph.

William Manchester, writer-in-residence at Wesleyan University, is the author of many books, including "Goodbye, Darkness" and "The Last Lion: Winston Spencer Churchill -- Visions of Glory, 1874-1932."