London — Forty years ago I began an article casually: ''I took an airplane the other day and came to Britain. I wanted to see and hear for myself how the British react to the war. Here I am and this is what I found out.''
That was Sept. 15, 1942, and superficially it could be used again -- word for word - for there is a Falkland Islands war going on. So could the next paragraph , with the exception of two small words:
''London is outside the window now as I write this. A barrel organ is playing a last year's American popular song. A British double-decker bus rumbles by. A British bobby in a tin hat cycles past, his raincape neatly folded over his left shoulder, his lunchbox strapped to the rear. He is pedaling home to the missus. It is all the same. Britain is still Britain.''
The words that have to be changed of course are tin hat. Nobody hereabouts has to wear metal helmets today, thank goodness, during the miserable dispute with the Argentines. There is a faint whiff of resemblance to 40 years ago, but it goes mostly into intangibles. Back in 1942 it was stark and brutal:
''Overhead big antiaircraft balloons ride in the sky. Every pane of glass in that rumbling bus is taped. The crowds are filled with soldiers carrying gas masks and rifles strapped over their backs. Last night as I walked home I saw the moon through a gaping skeleton of a once-famous London club. This afternoon I passed a place in the heart of London where the basements of three bombed houses have been turned into a supplementary reservoir for the fire department. You can see fireplaces sticking out of the walls on the side.
''In this bomb-made reservoir, by the way, a wild duck has moved in, hatched eggs, and is raising three young ducks right in the heart of London.''
No wild ducks today. No taped windows, no rationing. But Sunday when I left Bayswater Road, Campaign For Nuclear Disarmament marchers were going by: I stopped and watched them, thinking soon they would pass. But they came on and on , and the police had cordoned the avenue. As they straggled by there was some effort at unified chanting, an occasional gruesome costume depicting war, and thousands of placards.
They were well behaved, good natured. In the crowd an extraordinary number of perambulators were pushed along in what looked like a Sunday outing. If there was a hint of menace in the city it came from the clouds: The sun was shining, yet there was an almost constant rumble of thunder in what has been one of London's warmest spells.
I joined the crowd. We all went to Hyde Park. The antiwar leaders estimated a quarter million; the police estimated 115,000. I made no estimate, because you couldn't tell with the gathering spread out over the big park.
The mood was the important thing. It wasn't sullen or angry or menacing (despite that constant mutter from the sky). It was generally good-natured, concerned, curious, there was a Punch-and-Judy show going on in the middle of it , and racing children obviously on holiday. Far off, from an elevated platform, the speakers were haranguing, but it was hard to hear them above several helicopters that kept going over. Simultaneous protests were being made all over Europe, we were told.
If I got the sense of the crowd (and who am I, an American, to make the judgment?), there was an ill-defined uneasiness -- a kettle on the fire a long way from the boil.
A composite: The hospital workers were parading for a 12 percent wage increase; the Labour Party wanted votes; a rosy-cheeked infant in a pram seemed to be embracing a sign from a communist cell; everywhere were placards reading ''No cruise missiles''; a group of Iranians, Chileans, and Greeks denounced ''US imperialism: domination or destruction.'' What was this US imperialism? An article purporting to explain El Salvador had the facts all wrong: It linked Ronald Reagan with Margaret Thatcher.
The fact is that the world has gotten more complicated, more difficult, yes, even more disturbing in a way than 40 years ago, though (thank goodness) the immediate stakes are vastly less. Danger was terrifying in 1942: There was hardly a window that was not taped against bombs.
There was hardly a window that was not drawn at night against blackouts. At night the crowds moved along through eerie streets that were almost dark, but they were laughing crowds.
Yes, they laughed. There will always be laughter in an English crowd. It will bring along its prams to fight the A-bombs.
As I made mental notes, the rumble of thunder seemed to come from all directions. It would surely rain. I had better get out.
Was there a judgment for all this? Obviously anxiety is widespread: Britain must deal with the Falklands invasion, most people agree, but what then? It will be terribly costly. Who will pay the bill? What should their attitude be to President Reagan - approval or condescension?
Significantly the prestigious Sunday Times has just reprinted the climax of the passionate antinuclear dissertation, ''The Fate of the Earth'' by Jonathan Schell. Some papers warn Mrs. Thatcher, others applaud. Forty years ago it was simpler: taped-up windows but national unity. Today people sleep safe but dream about the bomb.
Here comes the rain: time to get out.