Nikolai Tolstoy is a tall, sandy-haired, blue-eyed, affable fellow who is more English than the English, people say, except for his personal wolfhound who is Irish.

A writer and a scholar of sorts, though he has no academic post, he lives agreeably in Somerset in the south of England with his wife and two young daughters on eight acres with a pleasant old house on it. People say you step back 200 years upon entering.

Tostoy (his great-grandfather was a cousin of the novelist) met his wife on a battlefield, he observed casually.

Of course one has to meet one's future wife somewhere.

"The siege of Warwick Castle," he said, during a reenactment of a battle between the Cavaliers and Round-heads. Young Tolstoy has a great fondness for the restaging of ancient battles and with some wryness points to a scar over his right cheekbone. You get these people reenacting battles, even though their intent is historical drama rather than enthusiastic slaughter, and someone is likely to get hur by a stick or twist an ankle in a ditch.

But in that great siege, Tolstoy met his wife, who was racing about in the skirmish and much too pretty, Tolstoy thought, to be soldier. One thing led to another.

It's never been far from his central consciousness that except for battles and wars he would have been Russian, not English.

He was born in Kent, but to a Russian household, and "if Russia were a civilized country, I'd move to St. Petersburg tomorrow."

But what, he sometimes wonders, if then he got homesick for England?

In the interest of common sense he has a way of seeing more than one side to a question.

He will lecture at 7:30 tonight at the National Archieves auditorium on a subject endlessly close to his heart and far removed from his country life of walks with his hound: the enforced repatriation of 2 million people to the Soviet Union following the collapse of Germany in 1945.

His book, "The Secret Betrayal," came out in England 18 months ago, and now has an American publisher, Scribner's and a fellow from Hollywood has approached Tolstoy about making a movie of it. Tosltoy is suspicous of Hollywood treatments.

The tragedy, as Tolstoy sees it, all began with the Yalta meetings of Stalin, Churchill and Roosevelt. They agreed that all Soviet citizens would be sent home after the defeat of Germany.

Sounded fine at the time.

But a total of 5 million people were involved, as Tolstoy reckons the number. Three million were tended to one way or another by the Red Army, he calculates, but 2 million remained to be sent back by the victorious Allies.

Many went home voluntarily, of course, but many did not, and Tolstoy's book examines in much detail how this happened.

The Russians (to use a brief term for many who never considered themselves subject to the Soviet state) were German prisoners of war or forced labor imported by the Germans.

Many considered themselves anti-communist freedom fighters, many fought in German uniform as part of German military units, and some had never lived in the Soviet Union at all, or were born to fugitives from the Russian Revolution.

To the Soviet state, these people were traitors, and Tolstoy does not suppose they were all splendid folk.

But he does argue that many were simply returned by the British and Americans with the knowledge that they would be killed or tortured or face slave-labor camps, and that some of these were examples of outrageous injustice never contemplated by the Yalta agreements.

A number of British and American soldiers objected to forcing them to the Soviet Union, including Eisenhower, but few were saved, Tolstoy maintains.

"There were the usual arguments, that in the confusion of Europe all these people could not be carefully screened. Or that the Yalta agreement had to be kept, no matter how distasteful it was working out. or that these people being sent back were war criminals who deserved no sympathy. Or that it was beyond Allied power to sort out all the wrongs of the Soviet Union and right them."

But this doen no explain, he argues, the bending over backwards, or even the seeming eagerness, with which the other Allies cooperated with the Soviets in turning over people who had sound claims to asylum.

Tolstoy says none of the policy figures would allow him to interview them, and he says the full story of their motives and reasoning are not known even now.

If the other Allies kowtowed to the Soviets in an effort to establish post-war harmony, Tostoy suggests it didn't work out that way, after all.

"And there remains the question of just how much suffering and injustice can be justified in pursuit of any national policy or aim."

There were the Nuremberg trials, he mentions, in which it was thought no excuse that Nazis were "following orders," and Tolstoy sees an analogy with Allied behavior in which many believed it was wrong, totally wrong, to repatriate people almost certain to be killed or worse.

The exiled novelist Alexander Solzhenitsyn said of Tolstoy's book that "finally the history of a curel betrayal on the part of the West of millions of helpless people is being told and exposed"-not that it is of any help now to the victims.

Tolstoy mentions that he had an ancestor, Count Peter Tolstoy, who was chosen by the Czar Peter the Great to lure back his son from Naples. The czarevitch, Alexei, had sought refuge from his fathers's violence, and it was Tolstoy's job to persuade him to return to Moscow.

The young prince believed some of the promise held out to him and returned. He was murdered at the czar's order, young Tolstoy recounts, and this early example of repatriation has never quite left his mind, nor his ancestor's unscrupulous part in it.

"It was simply a book I had to write, that's all," he said over a cup of tea at the Archives, where he is exploring papers relevant to this subject.

The book roused some interest in England, he said, and perhaps it will in America.

Tolstoy is tall and trim. He delights in talking, and despite his grim subject he is full of humor. Even the book includes some remarkable blends of honor and comic opera, as when the good folk of Liechtenstein thought the Russian refugees were an invading army.

He has received no threats, he said, though he told his wife to pay no attention if she started receiving photographs supposed to show him in incriminating postures with women.

"Did she receive any" he was asked.

No. But it's just as well to be forewarned.

Once, he said, before he was married, he and a friend approached two Finnish girls in London's Piccadilly Circus, to the envy of some fellows standing around but not knowing how to approach the girls.

One of them grabbed Tolstoy's top hat, and in the scuffle the girls vanished but were found a few blocks away.

"I told them," said Tolstoy, "that there was a frightful struggle going on in England between the classes and that it was necessary to cane the lower classes every day. I sometimes wonder what they made of that."

"It's probably all in some dossier in Moscow by now," it was suggested to him.

"Then it's in safe keeping," Tolstoy said. "Like the Germans, they never throw any paper away."

Not that they have shared any of their repatriation documents with Nikolai Tolstoy. CAPTION: Picture 1, Nikolai Tolstoy; by Harry Naltchayan-The Washington Post; Picture 2, Nikolai Tolstoy; by Harry Naltchayan-The Washington Post