LONDON -- It all so seemed so rosy in the stately Anglo-U.S. garden, however forced, just a few weeks ago.

U.S. President Donald Trump was being feted by British royalty and like-minded politicians, though the protesters decrying the American leader's visit were loud and in great numbers in London's Trafalgar Square once again.

The Second World War sacrifice and victory that came 75 years ago on the French beaches of Normandy on D-Day were marked with deep-seated mutual admiration and respect.

Then came the dreaded diplomatic cable leak.

Kim Darroch, the British ambassador to the U.S., branded the Trump administration "dysfunctional" and "inept." The unvarnished views caused a furious tweetstorm of insults in reply from the White House. This culminated in Trump saying they would no longer deal with Darroch, dismissing him as a "pompous fool." Darroch announced his resignation on Wednesday.

The spat comes at a sensitive time for both countries, with Britain about to get a new prime minister who will need to deal with the Brexit issue, and the U.S. speeding toward the 2020 presidential election.

Here's a look at some of the other low points in the "special relationship" that has afflicted the great trans-Atlantic allies over the decades.

THE COLD WAR AND DEFECTING BRITISH SPIES

The greatest shock to the U.S.-U.K. alliance came in the early chapter of the Cold War and left a damaging trail in both political and intelligence realms for many years that followed.

The Cambridge ring of five spies and diplomats passed information to the KGB in Soviet Union. Most infamous perhaps of all was Kim Philby, an MI6 officer, who began spying for the Soviets in the 1930s and defected there in 1963.

In several of British novelist John le Carre's books chronicling the period that followed, based on his own experiences as a British spy in the 1950s and 1960s, references abound to the American "cousins" espionage circles still not trusting the British.

THE SUEZ CRISIS

One of the most serious crises to beset London and Washington came at the crossroads of a dying British empire and the exponential growth of America as a superpower in the wake of World War II.

In 1956 in the Suez Canal, which connects the Mediterranean Sea and the Red Sea, Egypt's pan-Arab leader, Gamal Abdel Nasser, nationalized the canal to Britain's fury. The British joined forces with France and Israel in a clandestine operation to take control of it.

Worried about a potential Soviet intervention, U.S. President Dwight Eisenhower warned the coalition to withdraw.

In a humiliating climb-down the government of Prime Minister Anthony Eden, a man forever looking for his own Winston Churchill moment, did as he was told and his premiership ended in ignominy shortly after. Britain was no longer a global power.

THE VIETNAM WAR

Prime Minister Harold Wilson had a huge conundrum in the mid to late 1960s when his government overlapped with that of President Lyndon B. Johnson: at issue was the United States' prosecution of the war in Vietnam.

As a left-of centre Labour leader, Wilson did not want to directly support Washington, nor did the British public whose opposition to the war was significant.

The "special relationship" was heavily strained as an exasperated Wilson was purported to have said in private regarding Washington's concurrent economic support, "You don't kick your creditors in the balls!"

THE IRAQ WAR

Although President George W. Bush and Prime Minister Tony Blair were in lockstep and "shoulder-to-shoulder" from the 9-11 attacks onward, the war in Iraq faced huge protests and discontent in Britain, where many thought Blair was giving Bush a fig leaf to attack without a U.N. mandate.

The false intelligence that was used as a pretext for war over Iraq's alleged weapons of mass destruction has tainted Blair ever since. He remains one of the more loathed leaders in modern British history.

TRUMP AND BREXIT

Trump has made clear his displeasure over outgoing Prime Minister Theresa May's handling of Britain's exit from the European Union. His sharp criticism over the past three years, that she didn't follow his advice, seem to have been tempered when he was welcomed on a state visit this spring.

Trump even fulsomely praised May, saying she had not received the credit she was richly due for her tenure as premier. That all blew up in smoke after the diplomatic cables were leaked.

Trump went back on the attack after May gave her ambassador her full backing: "I told Γåòtheresa--may how to do that deal, but she went her own foolish way-was unable to get it done. A disaster!"

Now, a new British prime minister -- either Boris Johnson or Jeremy Hunt -- will be in place in two weeks with a plate overflowing with Brexit woes and an American president only to eager to have his view on what should be done and who should be doing it.