“MARGARET THATCHER here.” “If I were there, Margaret, I’d throw my hat in the door before I came in,” replied Ronald Reagan. It was October 26th 1983. The United States had just entered Grenada, a Commonwealth island-state in the Caribbean. The prime minister had opposed any action, but just woken to the news that American marines had invaded while London slept. In the now-public transcript of the ensuing call, the brutal architecture of what Britons like to call the “special relationship” is laid bare, Reagan’s polite superiority crackling and sparking on the phone line like a faraway thunder storm.

For America, the alliance has long rested on three pillars. One: the historical links and shared values between the two countries. Two: the chemistry between their political and cultural elites. Three: the case-by-case alignment of their interests. All of which puts Britain in an inner circle of American allies, along with Canada, Israel, Germany, Japan and Australia.

For some excitable politicians in London, however, that is not enough. For them, a fourth pillar exists: a common foreign-policy doctrine evolving in lockstep; a bubbling elixir of mutual admiration. This odd blend of chest-puffing arrogance and simpering insecurity is writ large in talk of Britain being “Greece to America’s Rome” (as a few old fossils still put it) and using its place in Washington to “punch above its weight”. Popular among those Eurosceptics who cherish an “Anglosphere” of like-minded English-speaking nations, it imagines a Britain not just whispering to America at the summit table, but staying up late with it afterwards, sipping scotch in wing-backed chairs and surveying the geopolitical horizon.

The belief in this fourth pillar waxes and wanes, but is always present. It was there in Thatcher’s disappointment during her call with Reagan in 1983, in Tony Blair’s confidence in his ability to shape the Bush administration’s response to the September 11th attacks, in Gordon Brown’s humiliating dash through the basement kitchens of the UN in 2009 to buttonhole Barack Obama about the financial crisis. Yet every time the fourth pillar has crumbled before their eyes, British panjandrums have reacted with fresh shock. They did so when Bill Clinton granted a visa to Gerry Adams (a militant Irish Republican) in 1994, when George W. Bush ignored Mr Blair’s entreaties about Israel’s invasion of Lebanon in 2006 and when Mr Obama upbraided David Cameron about the BP oil spill in the Gulf of Mexico during a visit to Washington in 2013.

Donald Trump’s election has exemplified this inability to learn lessons. Britain’s press responded with a symphony of British exceptionalism: Mr Trump would be sympathetic; Britain might even join NAFTA; the Trump administration would stand behind it in the coming Brexit talks. In a speech on November 14th Theresa May drew flattering comparisons between Britain’s vote to leave the EU and America’s election shock (both, she deduced, corroborated her argument that globalisation needs saving from itself). Meanwhile Boris Johnson skipped an emergency summit of EU foreign ministers to accuse them of a “whinge-o-rama” about a “liberal guy from New York”. When Nigel Farage, a prominent Brexiteer with close links to the American alt-right networks that helped propel Mr Trump to victory, met the president-elect on November 13th various mainstream British voices suggested that he might become a conduit between 10 Downing Street and the White House. American politics may have experienced its greatest earthquake in decades, but still Britain’s cocky-nervous delusions prevail.

Soon, reality will dawn. For it seems that the Trump era will be dominated by brute national interests. And it is far from clear why that should mean America doing a trade deal with Britain ahead of other countries, why the incoming administration might rein in its otherwise protectionist impulses to help Britain forge other trade agreements, why a White House led by Mr Trump would help London apply pressure on the continental Europeans, or what leverage Mrs May has to curb Mr Trump’s pro-Russian instincts. Or why—when the incoming president has long railed against Europeans freeloading on his country’s armed forces—the transatlantic partnership can satisfactorily substitute for Britain’s nascent defence partnerships in the EU.

All of which could shove Britain back into the arms of continental Europe. An impetuous, inward-focused Washington only makes Britain’s allies in Berlin, Brussels and Paris more important (witness the exaggerated horror in the press about a BBC television interview with Marine Le Pen, a far-right politician with a shot at becoming France’s next president). Mr Trump’s alarmingly conditional commitment to NATO makes the EU defence structures so maligned by Brexiteers look wiser. The flimsy talk of “Anglosphere” values will probably ebb away as the incoming American president makes Britain feel ever-more European. Brexit will come to look more, not less, short-sighted.

Don ask, Don tell

To be sure, Britain needs to do what it can to build links with the next White House. Britain’s military and intelligence complexes remain integrated with America’s. Pillar One of the alliance still matters—and is in jeopardy, Mr Trump having questioned the rules-based, institutional world order that has bound the two countries and their allies together for decades. So does Pillar Two: Mrs May, Mr Johnson and their advisers have all been rude about the president-elect and must now patch up the relationship. But the basic truth remains. Mr Trump will probably be an unabashed Pillar Three president, enraptured by the national interest and unmoved by transnational affinities. His presidency will thus expose Pillar Four as the sentimental chimera it has always been. If the next years do not teach Britons about the mercurial reality of the special relationship, it is hard to imagine what will.

Economist.com/blogs/bagehot