London — The special relationship between Britain and the United States is an intangible factor in world affairs that manifests itself most strongly in times of stress.
It is an undefined relationship based on emotion and common origin rather than formal treaty, but any third nation that ignores it does so at its peril. This relationship is being examined again closely in the aftermath of the Falklands crisis.
At a critical moment the US sided unequivocally with Britain. It declared that the Argentine junta's invasion of the Falklands was an act of aggression that could not be countenanced under international law.
The US made its position known awkwardly with a dazzling display of maladroitness at the United Nations: UN Ambassador Jeane Kirkpatrick cast a veto June 4 on a Falklands cease-fire resolution in the UN Security Council, only to state moments later that the US meant to abstain.
US declarations of support for Britain came with an implied caveat: an appeal to the British to proceed ''magnanimously.'' But there was no question of the central point: Even though it would cause temporary ill will in Latin America, the US would back Britain on the moral issue.
The intangible US-UK relationship lies somewhere beneath the surface, and it remains even when the two countries bicker. They love to admonish and lecture each other and to wonder aloud at each other's unseemly ways. But generally these are family quarrels. The two relatives sometimes frustrate, surprise, and even aggravate the other; they also interest, amuse, and inspire.
Each is more confident in a moral venture if it has the other's tacit support. Often at the end of a joint venture, however, history shows an element of disappointment as the two countries settle again to go their separate ways.
* In World War I the US sent 2 million armed men to Europe, and then rejected the League of Nations.
* In World War II American and British forces went ashore together on Normandy beaches, but at the end split over decolonization of the Third World.
* Now in the lesser conflict of the Falklands the US sides with Britain, but the question rises once more of what comes next, where do we stand to each other?
The relationship of everyday Englishman and Americans can be one of the most pleasant things in the world. In this turbulent summer each is a little on edge, at first looking for signs of concealed condescension, but this is soon gone. Where is that British reserve and hauteur we were supposed to find? I think it faded out in two world wars and belongs to the Victorian novelists. The American visitor is impressed by the quality of British radio and television with a minimum of commercial advertising. After World War I it was the other way - movies came from Hollywood and were shown all over England. Today the British broadcast shows are tops.
Some of the best serials and dramatizations come from BBC, which also has sent British productions to Broadway.
There is a continuous political process in both countries, meanwhile, of accommodating themselves to world changes. British postwar history has been the adaptation to reduced power and a need to act in concert with allies. Simultaneously, the US is learning that it must share the nuclear paramountcy with the Soviets and had better look for international support.
Some deny there is a special US-UK relationship. They are wrong. I saw it dramatized at the White House a week after Pearl Harbor. Reporters jammed around President Franklin D. Roosevelt's gadget-strewn desk in the Oval Office, but he wasn't the center of attention. Winston Churchill had come over unexpectedly; he was in the room.
''We can't see you,'' we yelled with unrestrained excitement.
He climbed on his chair while Roosevelt rocked and we cheered. He was stocky, he was not very tall - could this be the world figure we had read about? We were not long in doubt. He thrust out his jaw at one of the shouted questions and pronounced the word ''Nazi'' with a venom and contempt I have not heard equaled. Suddenly we understood everything. Yes, the special relationship existed.
Writing in Time magazine May 1 on the Falklands crisis, columnist Roger Rosenblatt says, ''There is no nation in the world that the American people value more highly than Britain, none for which they feel deeper personal and moral kinship, none for which they would sacrifice more, including their lives and none on which they so depend for precisely the same attitude.''
Probably most Americans haven't thought of it in just those terms, but would quickly assent if some crisis arose.
It has been so for a long time. Two GIs stopped me in London in World War II, standing lost in Trafalgar Square near the Nelson monument. All around was the English crowd - civilians, soldiers, and bobbies in helmets. There was no mistake about these two.
''Say, mister,'' said one, ''could you tell us the way to Westminster?''
It was pure Bronx accent and sounded grateful to my ears. I couldn't help myself.
''Hiya, Buddy!'' I responded, ''I'm one, too.''
''No kidding?'' exclaimed the first.
''No kidding?'' echoed the second.
''It's the real McCoy,'' I said, giving the countersign. We shook hands. After the formalities I asked how things were coming?
''It's the way they talk,'' complained the shorter one, ''it gets me.''
''Oh, you'll get used to it.''
''Man, I'll be doing it. Imagine taking that back wit' me to thoity-thoid street! . . .''
Today, many things are bringing the two countries together again, but other matters remain inexplicable.
The nations show affection for each other. On Massachusetts Avenue in Washington my bus passes the indomitable figure of Winston Churchill and his victory sign before the British Embassy. In London, Franklin Roosevelt has a better memorial in verdant Grosvenor Square than he does at home.
Still, to many British, some aspects of American life are hard to understand:
* How can America accept its monstrous crime rate when in England the police do not even carry firearms?
* Isn't it dangerous to leave treaty-veto power in the hands of one-third plus one of the US Senate - a situation that kept America out of the League of Nations in 1920 and the other day blocked submission of the SALT II treaty?
* Isn't it unfair to expect American presidents to ''govern'' when they lack the power (given to every British prime minister) to formulate their budget, subject to electoral test?
Some parts of the British system are also hard to rationalize in America:
* The British House of Lords may be a delightful anomaly but it is still a source of wonder across the Atlantic, as is the The Times's chatty ''court circular.''
* Parliamentary output might be improved a bit by the introduction of stronger committees like those in the US Congress.
* There seem an extraordinary number of strikes, stoppages and class discontent in Britain. Is this an offshoot of the welfare state or does it indicate some deeper, basic social malaise, a lack of individual and national self-confidence?
What is the state of the ''special relationship?''
I think it is closer than ever. It embraces the group of English-speaking countries who share the same values as well as personal and moral kinship. They also like to think they share the same language. By the time the Englishman in New York learns to look to the left instead of the right in crossing a street, and the American in London finds that an ordinary ''drugstore'' masks over here as a ''dispensing chemist,'' they have made a beginning.