The only certainty about President Donald Trump’s first visit to the United Kingdom is that it will unloose a fresh torrent of clichés about the “special relationship” between Britain and the United States.

It is certainly true, or has been through the past seven or eight decades, that the two nations share many interests and values that have advantaged both to pursue in harness. But the besetting sin of some British people, including successive prime ministers, is to delude themselves that sentiment influences U.S. behavior—now or over the past century.

Professor Sir Michael Howard once wrote on wartime attitudes: “It is never very easy for the British to understand that a very large number of Americans, if they think about us at all, do so with various degrees of dislike and contempt… In the 1940s, the Americans had some reason to regard the British as a lot of toffee-nosed bastards who oppressed half the world and had a sinister talent for getting other people to do their fighting for them.” Contemporary opinion polls support his view.

Among the foremost of Winston Churchill’s achievements was creating a legend of Atlantic unity in the face of an anti-Americanism widespread among British people—and especially their ruling class—and mirrored by animosity on the other side of the pond, for reasons suggested by Howard.

Churchill deployed a magnificent edifice of rhetoric, climaxing in his 1946 Iron Curtain speech at Fulton, Missouri, in which he called for a “fraternal association of the English-speaking peoples…a special relationship between the British Commonwealth and Empire and the United States.”

Yet in private throughout the war, he fumed and railed about the ruthlessness of U.S. policies. Arms and supplies shipped to Britain in 1940-41 required payment on the nail and thus liquidation of British assets in the U.S. at fire-sale prices. The prime minister wrote to Roosevelt on December 7, 1940, warning that if the cash drain persisted, “after the victory was won with our blood and sweat, and civilization saved and the time gained for the United States to be fully armed…we should stand stripped to the bone. Such a course would not be in the moral or economic interests of either of our countries.”

I have always thought it significant that Roosevelt, when responding, never addressed this point. He was most anxious that Britain should not lose the war, but never displayed the smallest interest in its fortunes thereafter. The 1941 Lend-Lease agreement, sustaining the flow of weapons and supplies when the Treasury had exhausted the nation’s realizable financial resources, came with conditions so stringently constraining overseas trade that London had to plead with Washington for a concession to enable Britain to pay for Argentine meat to feed itself. Postwar British commercial aviation was hamstrung by Lend-Lease.

Anthony Eden, Churchill’s foreign secretary, wrote that “our desperate straits alone could justify its terms,” and only those same straits could have persuaded the prime minister publicly to applaud Lend-Lease’s “unselfishness.” Montagu Norman, governor of the Bank of England, wrote: “I have never realized so strongly as now how entirely we are in the hands of American ‘friends’ over direct investments, and how much it looks as if, with kind words and feelings, they were going to extract these one after another.”

I share the view of Churchill’s biographer Roy Jenkins that the absence of Britain’s leader from Roosevelt’s funeral in April 1945 reflected not supposed duties of state, but instead private bitterness about the slights Churchill believed that the Americans, and Roosevelt personally, had inflicted upon their battered, weary, bankrupt ally. It was painful for the British people to behold the U.S. as the only nation to emerge from the war with a handsome cash profit.

None of the above is intended to represent a wail of nationalistic self-pity. The 1942-45 military partnership between the two nations was an extraordinary success story. It worked wonderfully well at the operational level. Difficulties and jealousies mounted only in the upper reaches of command hierarchies. Its achievement is not diminished by injecting some unromantic qualifications, unpalatable to neoconservatives.

Since the Second World War, the United States has conducted its foreign policy on the principle that dictates the actions of all governments including our own: furtherance of national interests. The 1946 American loan—$3.75 billion or $51 billion at current prices, which alone made possible creation of Labour’s welfare state—was granted on tough terms, including insistence that in the following year sterling was made convertible, precipitating a run on the pound.

The imperatives of the Cold War, and Britain’s retention of the third most powerful armed forces in the world, sustained a close military relationship, especially in intelligence. The Americans respected the abilities of British civil servants and diplomats who sustained a key role in international diplomacy, and drafted many agreements. Sir Oliver Franks, foremost among mandarins and a brilliant 1948-52 Washington ambassador, wrote that the Anglo-American relationship “arose out of common aims and mutual need… It was rooted in strong habits of working together on which there supervened the sentiments of mutual trust.”

Yet Franks overstated the latter. Successive British governments, in their anxiety to sustain American goodwill, gave away many things too cheaply. For instance, allowing American nuclear-armed bombers to be based here and giving the U.S. access to cheap uranium in exchange for ill-defined promises of American goods, which were not forthcoming.

The Korean War, which erupted in 1950, generated new difficulties. The Americans demanded a level of military support which the Treasury and the British army, threadbare despite its residual paper might, struggled to provide. The Clement Attlee government proposed a rearmament program that would increase defense spending from 7 to almost 10 percent of GDP. The U.S. offered financial aid only if that figure was raised to 14 percent. In its desperation to sustain American goodwill, the Labour government sought to meet this target, though the promised aid never materialized. It was left to the Tories who took office in 1951 to cut back the rearmament program to 10 percent, though even this imposed an intolerable burden.

The veteran Cambridge economist Robert Neild expresses scorn that Labour chancellor Hugh Gaitskell “bowed to the U.S. and abandoned…responsibility for nurturing the recovery of the postwar British economy. Why this craven relationship with the U.S. has lived on is another and puzzling question.”

Neild’s last sentence seems hyperbolic because modern Britain has good reason to be grateful that successive governments paid the bills to sustain a common front with the U.S. through the Cold War. Yet he is right that British anxiety to please Washington has often generated embarrassments and sometimes humiliations.

The Eisenhower administration was justified in denying support to the indefensible 1956 invasion of Egypt, enforcing British retreat amid the threat of our financial collapse. But the desertion hurt. So likewise did the 1983 American invasion of the Caribbean island of Grenada, a member of the Commonwealth, without the courtesy of consultation with Margaret Thatcher‘s government.

British leaders should notice that when their predecessors have dared to think for themselves, consequences have generally proved less alarming than Downing Street feared. The first notable example was Vietnam. The Johnson administration was disgusted by Harold Wilson’s refusal to send troops to support the 1965 U.S. escalation of the war. Secretary of State Dean Rusk told a British journalist bitterly: “When the Russians invade Sussex, don’t expect us to come and help you.” In reality, however, the prime minister merely had to endure some unpleasant personal exchanges with LBJ.

The second revealing episode was the 1982 Falklands war. The Ronald Reagan administration, and especially its Secretary of State Alexander Haig and United Nations Ambassador Jeane Kirkpatrick, perceived the anti-communist front in South America, to which the Argentine junta adhered, as being of greater importance than Britain’s retention of an outpost of empire. Both worked to dissuade Margaret Thatcher from launching military operations, and to distance the U.S. from the British cause.

In the last days of the conflict, the president urged Thatcher to halt her task force outside Port Stanley before it inflicted absolute defeat on the Buenos Aires regime. In a chilly telephone conversation (on the British side at least), the prime minister rejected Reagan’s demand, saying “we have lost too many men, too many ships.”

U.S. Defense Secretary Caspar Weinberger, an uncommonly staunch anglophile, authorized the provision of important aid to British forces, in the form of signals intelligence, fuel, Sidewinder missiles and use of the U.S. air base on Ascension island. This proved a rare moment in the postwar relationship, wherein America acted against its own perceived interests to assist a unilateral British purpose. It remains significant, however, that Weinberger had to defy his administration colleagues in order to do so.

The good news was that, in contrast to the 1956 failure at Suez, Britain’s Falklands success won American public applause. Resistance to Washington’s wishes did no lasting harm to the relationship.

The events of the past 80 years are familiar to historians and diplomats. What is surprising is that modern prime ministers nonetheless cling to expectations of gratuitous American goodwill—and wring their hands when this is unforthcoming. Tony Blair expected support in pushing Israel towards a settlement with the Palestinians in return for British participation in the 2003 U.S. Iraq invasion. He was shocked when this failed to materialize, though nobody else was.

One of Blair’s closest associates, a few months after the war, expressed frustration that in a range of bilateral negotiations, for instance on civil aircraft landing rights and access codes to defense technology, little or no progress was being made. “We’ve stuck out our necks a long way for the Americans,” he said in my hearing, “and it seems tough that we get no payback.”

Yet it was ever thus, and has become more so now that generations of diplomats and politicians who served in the Second World War are long gone. U.S. courts routinely, and in a shamelessly nationalistic spirit, harrow British businesses—consider the evisceration of BP since the 2010 Deepwater Horizon oil spill. The new breed of Washington decision-makers is incomparably more interested in Asia than in Europe. Some may adopt a benign view of Britain as a theme park, but not for a moment do they view us as important.

Indeed, among the foremost reasons to suppose that Brexiteers are deluded about our future outside the European Union is that they cherish such an inflated vision of our global significance. Raymond Seitz, the last brilliant American ambassador to London, warned privately back in 1991: “Never forget that the United States is only interested in Britain in so far as Britain is a player in Europe.”

Moreover, a reality bears repetition because it is so often ignored by our politicians. The value of allies, throughout history and in modern times, is measured not by skill in managing royal weddings but by the military capabilities a nation can deploy against threats. While through GCHQ (Government Communications Headquarters) we retain impressive cyber resources, the hard power element now looks very soft indeed.

Sir Michael Howard, who though aged 95 remains the wisest figure I have ever known, reflected recently on the perilous condition of the liberal world order which his postwar generation created: “Perhaps it was just a bubble in an ocean… The special relationship was a necessary myth, a bit like Christianity. But now where do we go?”

Quite so. Days before Theresa May became prime minister in June 2016, I found myself sat next to her at a dinner party. After an evening of exchanging social nothings, I said as we parted that I hoped she would forgive me for offering one reflection, as a historian: “When you are prime minister you will fly to Washington, where you will be greeted by a red carpet and all the usual American courtesies, then give a press conference in the White House Rose Garden. It will all be incredibly thrilling but please, please do not join the long line of British leaders who delude themselves that the Americans will do us favors.” When, on entering Downing Street, one of Mrs May’s first acts was to offer Donald Trump a state visit, my wife teased me that I should have saved my breath.

We must always treat the U.S. and its leaders with respect, even when they fail to reciprocate. The greatness of the country, and what I would characterize as the American genius, demand it. We must strive to sustain a transatlantic working partnership, vital to the interests of western security, even as the alliances on which global stability has rested since 1945 totter, not least because of President Trump’s avowed lack of sympathy for them.

But if Winston Churchill stood at the prime minister’s side, he would be chief among those warning her, on no account, to expect any U.S. administration, even one less purposefully disruptive than today’s, to give the British a break because they love Fortnum’s, Stratford-upon-Avon or the color of her eyes.

Sir Max Hastings is a military historian and author of All Hell Let Loose: The World at War 1939-45. (The Times London / News Syndication)