LONDON – Joseph Kennedy, the American ambassador to the Court of St. James liked to take a short walk from his residence into the most gracious of London’s open spaces, Hyde Park. On Saturdays he took his oldest son, Joe Jr., and his youngest, Teddy, to a large pond in the park where Teddy sailed a toy sailboat, along with other children of the privileged families who lived nearby in the elegant streets of Knightsbridge. In its tranquility the park and its many little rituals of leisure in the fall of 1938 was a refuge from a bigger, ugly reality.

At the same time in Germany thousands of shop windows were being shattered, hundreds of synagogues were burning and Nazi mobs were targeting Jewish communities in the outrage that became known as Kristallnacht. Thirty thousand German Jews were rounded up and shipped to concentration camps in Buchenwald, Dachau, and Sachsenhausen.

The isolation of Saturdays in the park from this horror reflected the isolationism pursued by Ambassador Kennedy. Adolf Hitler’s territorial aggression and persecution of the Jews was a European problem, he argued, and the United States should not be involved. Sensible diplomacy, he said, would prove that you could “get along” with dictatorships like those in Germany and Italy and imminent in Spain.

Kennedy had supported the “peace” pact made with Hitler in Munich early that fall by the British prime minister, Neville Chamberlain. Even though Hitler was soon ignoring the terms of the deal Britain would be wise to keep humoring him – and not to listen to a “drunk and warmonger” named Winston Churchill.

It’s strange how the threads of distant history sometimes converge into both an unsettling memory and a modern alarm. This happened for me this week when it was reported that one of London’s great mansions, 9 Prince’s Gate, had been sold to a Saudi family for around $100 million and would be turned into an even more palatial development that could be worth at least three times that.

However gutted these premises are in the transformation to mega-mansion, including a “leisure complex,” two pools, wine cellar and an underground car park with its own elevator for the limousines, they will forever be haunted by the role of Joseph Kennedy immediately before World War II and the dark legacy it left for his family. In the 1930s Prince’s Gate was the American ambassador’s residence and the embassy, with a staff of 200 diplomats.

This week, too, as survivors of the Holocaust assembled at Auschwitz on the 70th anniversary of its liberation and, at the same time, the British marked the 50th anniversary of Winston Churchill’s death, the confluence of memories and nightmarish personal histories retold flowed into Europe’s fresh bout of agonizing self-analysis. Before going to a ceremony at Auschwitz the French president, Francois Hollande, reaffirmed to French Jews, “Your place is here, at your home” – as synagogues and Jewish schools in France were under permanent armed guard.

In 1938 Joseph Kennedy had a solution to “the Jewish problem.” The New York Times reported that he had worked out with prime minister Chamberlain a plan to ship all German Jews to Africa and other places in the Western Hemisphere under the joint administration of Britain and the United States. That was news to the State Department, which Kennedy had not consulted, and to President Roosevelt for whom Kennedy had become an embarrassing loose cannon.

Prince’s Gate was a row of classically proportioned Georgian town houses given as a gift to the American nation by J.P. Morgan, whose father and founder of the banking dynasty was the first resident. Under Kennedy it became a covert base from which he built and worked through a network of similarly minded influential people in an attempt to steer American foreign policy clear of another world war. Roosevelt was informed by J. Edgar Hoover at the FBI that Kennedy was telling people in Europe that his president’s policy “was a Jewish production” and that Roosevelt would be defeated in 1940.

One of Kennedy’s willing accomplices was Charles Lindbergh. The head of the German Luftwaffe, Hermann Goering, had shrewdly feted Lindbergh in Berlin as an aviation hero, and gave “Lindy” a personal tour of German airfields, carefully screening what the American was allowed to see. Lindbergh had also been given graphic briefings of what the Luftwaffe had achieved in the Spanish Civil War, supporting the fascists, by introducing the carpet-bombing of civilian populations.

Kennedy asked Lindbergh to report his findings in a paper that he, Kennedy, then gave to Chamberlain before he met Hitler in Munich. Kennedy boasted to the columnist Walter Winchell that Lindbergh’s report had significantly influenced Chamberlain’s decision not to challenge the Nazi annexation of Czechoslovakia. Kennedy sang to the same score as frequently as he could, persuading British political leaders that the Luftwaffe could level any European city it chose to within days. The British, he said, stood no chance against such a blitzkrieg.

Word of Kennedy’s views and lobbying had long ago reached the one man in London who seemed inflexible in his views of Hitler’s evil and his aims, Churchill. The columnist Walter Lippmann had told Churchill that Kennedy was predicting that the British would be defeated in a war with the Germans.

Churchill, said Lippmann, glowered through the smoke of his cigar and said, “No, the ambassador should not have spoken so, Mr. Lippmann. He should not have said that dreadful word. Yet supposing – as I do not for one moment suppose – that Mr. Kennedy were correct in his tragic utterance, then I for one would willingly lay down my life in combat rather than, in fear of defeat, surrender to the menaces of these sinister men.”

Although this may seem like familiar truculent rhetoric and vintage Churchill it’s important to note that at the time, before the outbreak of war, Churchill, in his early sixties, was a relatively fringe figure, leading a small group of politicians adamantly opposed to the Munich “peace in our time” delusions and pressing for Britain to rapidly rearmam. As Kennedy was regarded in the State Department and White House as a man who put his own business interests above all others, Churchill was not seen in London as a safe pair of hands to run the country in the event of war.

When Britain declared war on September 3, 1939, Kennedy was in a funk. “It’s the end of the world,” he kept repeating, “the end of everything.” He departed for leave in America soon after, where he kept insisting whenever he spoke that “There is no place in this fight for us.”

Roosevelt, however, made no move to replace him – to ensure that he could not directly play a role in the coming presidential election. Kennedy returned to London in February 1940, where his defeatism remained unbridled, insisting to everyone who would listen that the British would be “thrashed.”

In May Chamberlain’s government fell. And in the most fateful days ever in British history, after days of shifting alliances and factional disputes that threatened any sense of achieving national unity of purpose, Churchill emerged as prime minister.

From then on Kennedy had no audience. “The ambassador does not go out for dinner these days,” said one of his few remaining friends.

The extent to which he had become a pariah is shown in a comment by Lord Halifax, who had been Chamberlain’s foreign secretary and shared, with Chamberlain, the odor of having capitulated to Hitler and of encouraging the movement for appeasement. Nonetheless Halifax had no time for Kennedy. He noted in an official memo: “Mr. Kennedy is a very foul specimen of double crosser and defeatist. He thinks of nothing but his own pocket. I hope this war will at least see the elimination of his type.”

In the summer of 1940, when the Royal Air Force, in the Battle of Britain, stood alone against the Luftwaffe and Goering’s strategy to soften up British defenses before an invasion, Kennedy had learned nothing.

“The British have had it. They can’t stop the Germans and the best thing for them is to learn to live with them.”

On the contrary, the R.A.F. decimated the Luftwaffe and made an invasion impossible. In retaliation, Hitler ordered the nighttime Blitz on London. The people of London took terrible punishment but never wavered. Kennedy, always a compulsive womanizer, fled the capital to a hideaway in the country near Windsor that he shared with a girlfriend from Paris. Behind his back the British called him “Jittery Joe and “Run rabbit, run.”

On October 23 Kennedy left the embassy in Prince’s Gate, never to return.

Kennedy’s anti-Semitism was of a kind widely shared but not widely declared in the 1930s. It was all the more lethal because of its casualness – for the Nazis it created a general moral complicity that they knew they could exploit, and did, as they correctly judged that the defense of Jews was for millions of people not sufficient cause to go to war.

In one sense this was perhaps a strange prejudice for Kennedy to share. As the son of Irish immigrants to Boston he knew what it was like to struggle as part of an immigrant minority in a society dominated by New England Brahmins who felt it was their birthright to run everything.

Kennedy’s father-in-law, John F. Fitzgerald, who had one term in Congress before becoming the first Irish-born mayor of Boston, was famous for his put-down of the most lofty Brahmin of them all, Senator Henry Cabot Lodge. Fitzgerald led the opposition to a bill that required that all potential immigrants should be able to pass a test that included the ability to read the Constitution (sound familiar?). Lodge castigated him: “Do you think Jews or Italians have any right in this country?” “As much right as your father or mine” snapped Fitzgerald, “After all, it’s only a difference of a few ships.”

But once Joseph Kennedy had made his fortune and was established in the new generation of self-made tycoons Jews seemed somehow to occupy a permanent role as the excluded ones – for example, the Nazis’ ambassador in London reported to Berlin that Kennedy “understood our Jewish policy completely; he was from Boston and there, in one golf club and other clubs, no Jews had been permitted for the last 50 years.”

In that regard, Boston was no different from any other city or town throughout New England and Kennedy was no more egregious than many of his contemporaries.

It can be argued, of course that these prejudices were not conditioned by any anticipation of what the ultimate result of unrestrained anti-Semitism could be—genocide on an industrial scale. But once the charnel houses of Belsen, Buchenwald, Dachau, Auschwitz-Birkenau and scores of other death machines were revealed, to universal horror, the real sin of “casual” anti-Semitism was revealed: its indifference and lack of imagination. The Nazis were monsters but Kennedy and many others decided they could be negotiated with as though they were like those running a normal civilized state.

The word appeasement was in itself a form of euphemism. It didn’t come close to describing the moral depravity of trying to appease those who were clearly evil. And euphemisms, then and now, are the beginning of the political process of glossing over what is actually going on.

This point was powerfully made in the gathering that mourned the deaths of more than a million souls at Auschwitz. Roman Kent, a survivor, said “We do not want our past to be our children’s future” and he warned against “sanitizing” the record of the Nazis by the use of evasive words – for example, using “lost” to describe the 11 million who were liquidated in the camps, including 6 million Jews. “They did not perish in the normal sense of the word,” he said, “they were brutally and viciously murdered and burnt.”

Churchill never succumbed to euphemisms. From the assumption of Hitler to power in 1933 onwards, he viscerally felt the innate evil of the Nazis. As a result he spent years in the political wilderness while others sold their souls to avoid admitting the truth about Germany and its aims. Some of the commentary on the 50th anniversary of his death pointed out Churchill’s flaws, as though they somehow diminished his achievement. Flaws there were, but for those of us able to remember him as a war leader, albeit as children, his genius was to represent in his own voice and actions a national resolve that would not have been credible in any other kind of personality. That was the essence of his leadership. No other British politician of the day could match him. He was the man for the hour and proved it.

As for Joseph Kennedy, the war turned out to be a tragedy for his family. His eldest son, Joe Jr., was killed flying on a mission in Europe that he volunteered for. A treasured daughter, Kathleen, married into the English aristocracy but lost her husband in battle and then herself died in an air crash. John Fitzgerald Kennedy had a close brush with death in the Pacific war and suffered a crippling injury that dogged him for the rest of his abbreviated life. More tragedies were to come but the family’s public reputation was finally redeemed. The sins of the father will, however, always be indelibly attached to those years in the mansion at 9 Prince’s Gate, London.