The tale of malevolent spymasters, intricate tradecraft and cold-eyed betrayal reads like a John le Carre novel. But The Sword and the Shield (Basic Books) has the added twist of being a work of nonfiction, and last week its publication revealed secrets about the KGB's long-secret war against the West that made headlines around the world.

In Bexleyheath, south London, an 87-year-old great-grandmother, Melita Norwood, confirmed that yes, as the book charges, she stole atomic secrets for Moscow for more than 40 years. Authorities in Western Europe and the U.S. learned that the KGB had easily intercepted revealing faxes from major defense firms and buried booby-trapped caches of arms, radios and uniforms to help saboteurs. In Paris, Le Monde followed up with a story charging that the current Socialist Party leader in the Senate, Claude Estier, worked secretly for the Soviet bloc starting in 1956. Estier called it a "tissue of nonsense."

The source of the storm is Vasili Mitrokhin, 77, who in 1972 was the officer in charge of checking, sealing and moving to a new headquarters 300,000 files kept by the KGB's foreign intelligence service. Disillusioned by the 1968 Soviet invasion of Czechoslovakia, he set about copying in longhand the highly sensitive files in his care and stuffing his notes in metal cases beneath his dacha. By his retirement in 1984 he had a trove of the KGB's deepest secrets, including agent names and accounts of assassinations and covert actions. In 1992 he arranged for British intelligence to whisk him, his family and his trunks of paper to safety. Spy hunters and prosecutors got first crack at the papers, and according to Mitrokhin's co-author, Cambridge University historian Christopher Andrew, a dozen probes of old spies are still active. Mitrokhin wanted to publish his files to reveal to the world the paranoia, cynicism and abuse endemic in Soviet power - the ultimate dissent from a system that died because it could not accept any.

Like so many Soviet officials who washed their hands of the system during the Gorbachev era, Vasili Mitrokhin dated the beginning of his loss of faith from the time of Nikita Khrushchev's "secret speech" in 1956, which exposed Stalin's abuse of power, raising for the first time the question of the regime's purpose, promising serious reform.

Many such people have averred that during the three long subsequent decades they lived dual mental lives, serving the state and advancing their careers, while also surreptitiously nourishing the seeds of the dissent that would one day burst forth as the demand for fundamental political reform.

Mitrokhin's extensive reading of KGB files, especially once he was made head of the KGB's archives in 1972, brought home with even greater clarity the criminality of the regime to which he had devoted his labour, and it led him to set about collecting and annotating his own record of the files under his control - stretching back to the time of the Bolshevik revolution and covering most major aspects of the KGB's work throughout the world - with the aim of one day bringing it to light in Russia.

He had joined the KGB in 1948. He served as an undercover agent in the Middle East and at the Olympic Games in Australia in 1956, and in the late 1950s began working in the service's archives. Posted on an archival assignment to East Berlin in the second half of the 1960s, he was close to the scene when the Soviet army invaded Czechoslovakia. This reinforced the disillusionment he was already feeling over the lack of political change in the Soviet Union.

From 1972 until his retirement in 1984 he was chief archivist. With the demise of the Soviet Union, he began to plan his clandestine departure for the West - clandestine because he would have in his possession an enormous haul of secret documents from the KGB archives.

In 1992, with a sample of what he had to offer, he walked into the British embassy in one of the Baltic republics (having been turned down by the Americans), and as a result was "exfiltrated" from Moscow to London, together with his wife and their son. The British Secret Service then organised the removal from his Moscow home of six aluminium trunks of notes, the largest and most comprehensive collection of Soviet secret intelligence materials ever seen in the West - as far as the public knows.

After seven years of meticulously hard labour, a big book called The Mitrokhin Archive (1999) was published. Co-authored with Professor Christopher Andrew, currently the official historian of MI5, the book is a model of the judicious use of archives and published sources.

English readers were surprised to learn that the most spectacular Soviet agent surviving in the UK was now an octogenarian grandmother. Melita Norwood had been betraying British nuclear secrets to the Soviet Union for 40 years, from 1937 to the mid-1970s. The Government decided, however, that it could not prosecute her so long after the event.

Then there was the so-called "Romeo agent", John Symonds, a detective sergeant in the Metropolitan Police, who, according to Mitrokhin, had fled Britain when faced with corruption charges and had been recruited by the KGB in Morocco. After suitable training, he was tasked with seducing female staff in foreign embassies to obtain secret information.

To discredit MI5, the KGB had planned to disrupt the 1969 investiture of the Prince of Wales; it also plotted to injure and disfigure the defectors Rudolf Nureyev and Natalya Makarova, in order to wreck their careers as ballet dancers. In the United States, the KGB claimed to have tapped Henry Kissinger's phone calls to President Richard Nixon, and tried to recruit Zbigniew Brzezinski, President Jimmy Carter's national security adviser. More information came out on a host of spies and suspects, as well as on the British agents Guy Burgess, Donald Maclean and Kim Philby.

At the time of publication, doubts were expressed about Mitrokhin's selection of material. Such doubts were inappropriate. As chief archivist, his job was to deal with whatever files arrived on his desk for processing, or whatever documents he needed to consult to complete a case. His main responsibility was the KGB's operations abroad, but since to process such cases often entailed reference to domestic concerns - especially personal data - the "product" was much wider in scope. But it was precisely the accidental nature of this process that produced the extremely varied and multi-faceted character of his collection.

Few have doubted that Mitrokhin accomplished a Herculean task, for a period of 12 years transcribing a mountain of documents, concealing flimsy copies in his shoes and taking them home, as it were from under the nose of his boss, Yuri Andropov, and burying them inside milk churns in his kitchen garden. Following the publication of The Mitrokhin Archive, his KGB Lexicon was published in 2002, and at the time of his death he was negotiating the publication of further studies based on the still untapped materials he had brought from Moscow.

Vasili Nikitich Mitrokhin was born in 1922 in Yurasovo in Ryazan Oblast, the second of five children. His father was an itinerant decorator who moved his large family to wherever he could find work. At 18 Mitrokhin entered an artillery school, but with the German invasion of the Soviet Union in 1941 he moved to Kazakhstan, where he studied for a degree, graduating in law after first reading history.

Towards the end of the Second World War, he took his first job, in the military procurator's office in Kharkov, Ukraine, then entered the Higher Diplomatic Academy in Moscow, a three-year course, which ended with his recruitment in 1948 into what was soon to be become the Committee of State Security, i.e. KGB. He said in an interview that when he joined the KGB in 1948 he was "looking for the New Jerusalem, but ended up at the Wailing Wall".

Vasili Mitrokhin, who died on January 23 aged 81, was the former KGB archivist whose defection to Britain in 1992 brought a treasure trove of Soviet secrets to the West.

Mitrokhin's archive consisted of a huge volume of material culled from tens of thousands of top-secret KGB files, which he had laboriously copied down over 12 years and hidden in tins and milk crates underneath his dacha. It contained detailed records of every operation the KGB had mounted from its inception in 1917 to Mitrokhin's retirement in 1984, demonstrating the extent to which the KGB had successfully infiltrated the West and the way in which it had oppressed the Russian people.

Among other revelations, the papers disclosed that more than half of Soviet weapons were based on designs stolen from America; that the KGB had tapped the telephones of American officials such as Henry Kissinger and had spies in almost all the country's big defence contractors. In France, at least 35 senior politicians were shown to have worked for the KGB during the Cold War. In Germany, the KGB was shown to have infiltrated all the major political parties, the judiciary and the police.

Also fascinating was the insight given into the absurd lengths to which the Russians were prepared to go to discredit those they regarded as ideological enemies. There was a plan to break the legs of Rudolf Nureyev, the ballet dancer, after he defected in the West in 1961. On one occasion a team of 18 KGB operatives was dispatched to the Philippines with instructions to ensure that the Soviet world chess champion, Anatoly Karpov, was not defeated by the defector Victor Korchnoi in the World Chess Championship. The methods employed including stationing a hypnotist in the front row of the audience, who stared intently at Korchnoi throughout the matches.

On September 11 1999 the archive suddenly became front page news when serialisation of The Mitrokhin Archive, the book written by Mitrokhin with the historian Christopher Andrew, began in The Times. The revelations that captured media attention were not so much the disclosures about KGB operations against Nato and the suppression of dissent within the Soviet Union, but human interest stories about Soviet spies in Britain. These included Melita Norwood, an 87-year-old great-grandmother from Bexleyheath - the "spy who came in from the Co-op" - who was exposed as having been the KGB's longest-serving agent in Britain.

The acquisition of the Mitrokhin archive was a huge coup for British intelligence, which had recognised the value of the material after it had been turned down by the Americans.

But the revelations proved an embarrassment to the authorities when it emerged that the identity of the spies had been known to the security services since 1992 when the Mitrokhin archive was handed over to the British authorities, but no action had been taken.

Mitrokhin's motives were the subject of much speculation. He did not defect for the money and was not being blackmailed; nor did he seem to enjoy his new life in the West. Some suggested that he had become embittered after being transferred from operational duties for the KGB to archives. But it is equally possible that his own explanation was the genuine one. He simply decided that Soviet Communism was evil and should be opposed.

In handing over his archive, the only condition he imposed was that his work should be made public as a record for the Russian people and as a warning to future generations.

The son of a decorator, Vasili Nikitich Mitrokhin was born on March 3 1922 in Yurasovo, in the rural Rayazan province of Soviet Russia. After leaving school, he entered artillery school, then attended university in Khazakhstan, graduating in History and Law. Towards the end of the Second World War, he took a job in the military procurator's office at Kharkov in the Ukraine.

Then an idealistic Communist, Mitrokhin entered the Higher Diplomatic Academy in Moscow and, in 1948, was recruited into the KI (the Committee of Information), the Soviet external service which was absorbed into the newly formed KGB in 1954.

During the 1950s he served on various undercover assignments overseas. In 1956, for example, he accompanied the Soviet team to the Olympic games in Australia. But later that year, after he had apparently mishandled an operational assignment, he was moved from operational duties to the archives of the KGB's First Chief (Foreign Intelligence) Directorate, and told he would never work in the field again.

Mitrokhin sometimes dated the beginnings of his disillusionment to Khrushchev's famous speech to the Communist Party congress denouncing Stalin, though it seems he may have been harbouring doubts for some time before that. For years he had listened to broadcasts on the BBC and Voice of America, noting the gulf between their reports and party propaganda.

Yet when he began looking into the archives, he claimed to have been shocked by what he discovered about the KGB's systematic repression of the Russian people. "I could not believe such evil," he recalled. "It was all planned, prepared, thought out in advance. It was a terrible shock when I read things."

When, in 1972, the archives were moved from the Lubyanka in Moscow to a new repository on the outskirts of the city, Mitrokhin seized his chance. Given the responsibility of checking and sealing about 300,000 files, he began making notes on the documents, which he smuggled out of the building in his shoes, trousers or coat. At weekends, he took the bundles of notes to his dacha and, after copying them out in longhand, buried them in tins and milk churns beneath the floor. Had he been caught, he would almost certainly have been executed.

Mitrokhin continued his clandestine activities for 12 years until his official retirement in 1984, when his boss, Vladimir Kryuchkov, congratulated him for his success in transferring the archives and his "irreproachable service to the state security authorities".

In retirement, Mitrokhin watched and waited, little expecting that he would ever have the opportunity to bring his archive to light. His opportunity came when the Soviet Union began to fall apart. In 1992, he obtained permission to take a holiday in Latvia. Taking samples of his archive with him, he walked into the American embassy in Riga and asked if he could defect. CIA officials at the embassy, struggling to cope with hundreds of Russian exiles trying to flee the crumbling Soviet Union, were not interested. They reasoned that Mitrokhin was not a spy, just a librarian, and the handwritten documents were probably fakes.

Mitrokhin then tried the nearby British embassy, which immediately recognised his importance and began to make arrangements to spirit him out of the country. These were initially hampered by the need to retrieve the rest of the archive, still buried under Mitrokhin's dacha. A plan was hatched involving six MI6 officers dressed as workmen, who unearthed six trunks of material and loaded them into a van. On September 7 1992, Mitrokhin, his family and his archive, arrived in Britain.

So successful was the MI6 operation that, for some time, it seems the Russian authorities were unaware that he had gone. Subsequently, they made a clumsy attempt to discredit the archive, by sending two apparent "defectors" to Western intelligence agencies who claimed that the KGB's successor, the SVR, had decided on a massive clear-out of superannuated agents and had chosen Mitrokhin to transmit their details to the West. By that time, though, it had become clear that Mitrokhin's material was far too valuable for the SVR to have handed it over willingly, and the "defectors" were soon exposed as Russian plants.

The publication of The Mitrokhin Archive in 1999 was followed by other publications, including, in 2002, Mitrokhin's KGB Lexicon.

But life in exile was difficult for Mitrokhin, who lived in fear that he might be stalked by vengeful former comrades. He spoke little English, had few friends and was devastated when his wife, Nina, died in 1999. Interviewers noticed a sadness hanging over him.

The Mitrokhin archive led to resignations, arrests and a few prosecutions around the world, though there are believed to be about 300 Soviet sources still living in Britain and America who have not yet been publicly identified.
Mitrokhin is survived by his son.

The former senior KGB archivist Vasili Mitrokhin, who has died from pneumonia aged 81, will be best remembered for his extraordinary achievement in noting down the contents of top-secret Soviet foreign intelligence files and, at great personal risk, smuggling them out of the secret police headquarters on almost every working day for 12 years.
The files ranged in time from the immediate aftermath of the 1917 Bolshevik revolution to the eve of the Gorbachev era in the late 1980s, and contained details of KGB operations in most countries of the world. Mitrokhin had access even to the holy of holies in the foreign intelligence archives - the files that revealed the real identities of the elite corps of KGB "illegals" living under deep cover abroad, disguised as foreign nationals.

When this private archive reached the west in 1992, it was described by the FBI as "the most complete and extensive intelligence ever received from any source".

Mitrokhin was born in Yurasovo, in Ryazan province, south of Moscow. As a child - and, indeed, later as a KGB officer - he was never happier than when he was in the Russian countryside, tending his vegetable patch, fishing and hunting. Throughout his life, his tastes remained simple; he preferred his own home-made vegetable soup to the menus of expensive western restaurants.

After graduating in law during the second world war, and spending three years at the Higher Diplomatic Academy in Moscow, Mitrokhin was recruited as a Soviet foreign intelligence officer in 1948. His first five years were overshadowed by the paranoid, final phase of the Stalin era, when he and his colleagues were ordered to devote much of their energy to tracking down the so-called Zionist and Titoist conspirators, whose mostly non-existent plots throughout the Soviet bloc obsessed the disturbed mind of the ageing dictator.

The first official repudiation of Stalinism came in Nikita Khrushchev's now celebrated speech to a closed session of the 1956 Communist party congress. Though considered too shocking for the mass of the Soviet population, the contents of the speech were debated for two days by the KGB party branch to which Mitrokhin belonged. No one present dared to ask the question he was convinced was in all their minds: "Where was Khrushchev while all Stalin's crimes were being committed?"

In the aftermath of the speech, Mitrokhin became too outspoken for his own good. Though his criticisms of the KGB's unreformed bureaucracy were mild by western standards, they led to his transfer, late in 1956, from operations to the relative backwater of the archives, where he served for the remainder of his career.

He continued to hope that the Soviet system might somehow reform itself. But when "socialism with a human face" emerged in Czechoslovakia during the Prague Spring of 1968, Soviet tanks moved in to restore the neo-Stalinist, one-party state. Henceforth, like many other dissidents, both open and undeclared, Mitrokhin concluded that the system was unreformable and would have to be replaced.

Over the next few years, his views were deeply influenced by the dissident struggle, which he was able to follow in both KGB reports and western broadcasts. "I was a loner," he later recalled, "but I now knew that I was not alone."

Though Mitrokhin never had any thought of aligning himself openly with the human rights movement, the example of the Chronicle Of Current Events, and other samizdat productions, helped to inspire him with the idea of producing a classified variant of the dissidents' attempts to document the iniquities of the Soviet system. Gradually, the project began to form in his mind of compiling his own private record of the KGB's foreign operations.

His opportunity came in 1972, when the foreign intelligence directorate left its overcrowded offices in the KGB headquarters near Red Square, and moved to a new, Finnish-designed building at Yasenevo, half a mile beyond the Moscow ring-road. For the next 10 years, he was to be in charge of moving the entire foreign intelligence archive, file by file, to Yasenevo.

While supervising the move, Mitrokhin was able to note whatever top-secret files he wanted. Initially, he smuggled out his daily notes on small scraps of paper hidden in his shoes. After a few months, however, he realised that the security guards at the new headquarters confined themselves to occasional inspections of bags and briefcases, without ever attempting body-searches. Henceforth, he made his notes on office paper, which he then took out of Yasenevo in his jacket pockets.

Every weekend, Mitrokhin buried the notes beneath the family dacha in the countryside near Moscow. The enormous risks involved in compiling his secret archive, which might well have ended with his discov ery, a secret trial and a bullet in the back of the head in an execution cellar, leave no reasonable doubt about the strength of his convictions.

After his retirement in 1984, he devised various schemes to smuggle his archive to the west. None proved practicable until the disintegration of the Soviet Union at the end of 1991 left the Russian Federation with, initially, relatively weak frontier controls between it and the newly inde- pendent Baltic republics. In March 1992, after unsuccessfully trying to contact the CIA, Mitrokhin took samples of his archive to the British embassy in Riga, which put him in touch with MI6.

Later that year, on the 75th anniversary of the Bolshevik revolution, MI6 brought his family - and his archive - to Britain, in an extraordinary operation whose details have yet to be revealed.

Late in 1995, I met Mitrokhin over tea in a conference room at MI6 headquarters, on the Thames at Vauxhall Cross. A few months later, we began writing a lengthy volume, based chiefly on the material he had smuggled out of Yasenevo, which was published in 1999 as The Mitrokhin Archive: The KGB In Europe And The West, and later widely translated. Only with the publication of this book did the existence of the archive, and Mitrokhin's escape to Britain, become public knowledge.

The sections of the book which attracted most media attention were, predictably, the human interest stories, such as the identification of Melita Norwood (quickly dubbed the "great-granny spy") as Britain's longest-serving Soviet agent. Understandably, Mitrokhin himself attached more importance to the chapters on the KGB offensive against the west, and its obsessional attempts to root out all forms of dissent within the Soviet bloc.

A second volume of The Mitrokhin Archive, dealing mainly with KGB operations in Latin America, Asia, the Middle East and Africa, is due for publication next year. Mitrokhin himself also published The KGB Lexicon (2002), which provides a fascinating insight into the KGB mindset, as well as its tradecraft and bureaucratic jargon. His study on Afghanistan, put on the internet by the Washington Cold War Inter national History Project, was the first of several works based on KGB files that he was preparing before his death.

Efforts by the media to track Mitrokhin down after the publication of our first volume were, happily, unsuccessful; he was too private a person, and had arrived in Britain too late in life - and with too little experience of the west - to have coped with the glare of publicity. He had, however, perfected the art of being inconspicuous, and travelled unnoticed the length and breadth of the United Kingdom on his senior citizen's railcard. After the tragic death of his wife Nina, a Russian doctor, from motorneurone disease in 1999, he flew around the world on his British passport.

While in Britain, scarcely a week passed without Mitrokhin re-reading his papers. Despite declining health, he continued preparing parts of his archive for publication until only a few weeks before his death.