Routine briefings at UN headquarters are rarely exciting, but the one of 11 April 1978 dropped a bombshell. Shevchenko, the spokesman noted, "has informed the Secretary-General that he is absenting himself from the office and, in this connection, he mentioned differences with his government".
It had been some two and a half years earlier that Shevchenko first decided to cast in his lot with the Americans, the climax of a long disaffection with his own country and government. Upon contacting the CIA, however, he learnt to his unpleasant surprise that he was required to remain in place; the international civil servant would have to sing for his supper, and earn sanctuary by spying. Slowly, Moscow's suspicions grew.
Finally, on 31 March 1978, came the cable of which every traitorous Soviet official abroad lived in dread, recalling him immediately for consultations, and "discussion of certain other questions". A couple of days later Shevchenko slipped from his Manhattan flat, climbed into a CIA car and was whisked off to a safe house in Pennsylvania to begin his second life.
His former masters, their fury matched only by their embarrassment, pulled out every stop to get him back. The KGB concocted wrenching letters from his family, and mingled promises of clemency with the most unsubtle of threats if he did not comply. To no avail. As Shevchenko was being debriefed in Washington, he learnt from a press report that his wife Lena had died in Moscow. Officially she had committed suicide. Shevchenko would always suspect she had been murdered by the KGB.
In some ways Arkady Shevchenko was an unlikely candidate to turn his back on his country. Born in Ukraine in 1930, the son of a doctor, he had spent much of his childhood in the relative paradise of the Crimea (where his father met Churchill, Roosevelt and Stalin at Yalta in 1945 while secretly evaluating the health of the dying US President). Shevchenko enjoyed the best the Soviet Union could offer: a prominent role in the Komsomol youth organisation, and then a place at the Moscow State Institute of International Relations, academy of the diplomatic elite.
He became a protege of Andrei Gromyko, the hugely influential and seemingly eternal Soviet foreign minister. Shevchenko accompanied Nikita Khrushchev on his famous visit to America in 1960, and from 1963 to 1970 served at the Soviet mission to the UN. After three years in Moscow as a senior aide to Gromyko, he returned as Under Secretary- General in 1973, aged just 43. By then he was one of the brightest stars of his diplomatic generation, surely destined for a senior ambassadorship, perhaps even deputy foreign minister. As a card-carrying member of the nomenklatura, he would - by Soviet standards - want for nothing.
Shevchenko abandoned it all. One reason was material, stemming from a first stunning glimpse of New York on an earlier official mission in 1958: "I had seen photographs," he wrote, "but nothing had prepared me for the impact of the towering city on the horizon" (and, even more pertinently, of the plenty in its shops). From that moment, he was materially hooked on the West. Spiritually, the constraints and dishonesties of the Soviet system, magnified for one who lived abroad, became too much to bear. In retrospect, Shevchenko's defection was inevitable.
Its actual importance has been much debated. Certainly, he does not rank with Col Oleg Penkovsky, or the KGB station chief in London, Oleg Gordievsky, or even Igor Gouzenko, the cypher clerk who fled from the Soviet mission in Ottawa in 1945 carrying evidence of Moscow's elaborate wartime spy rings in the West and of how America's nuclear secrets had been passed to Moscow. A natural self-promoter with no doubt of his own talents, Shevchenko may moreover have parlayed the information he brought into rather more than it was.
Nevertheless he was a notable catch. During his service as an American "spy" at the UN, he passed over details of Soviet policy on every major issue. As a lifelong specialist in arms control, Shevchenko provided precious insight into Soviet negotiating strategy for the disarmament talks that stuttered along in the late 1970s and early 1980s. Third, no defector has ever known as much about the high-level workings of the Soviet state, the inter- play between the Foreign Min- istry, the military and the omnipresent KGB.
By the end of his life, of course, most of this was an irrelevance. The Soviet Union had vanished, and the man whose 1985 autobiography, Breaking With Moscow, had been an international best-seller had been washed up, forgotten, on history's strand. When he died, he was labouring in obscurity on a study of Soviet foreign policy.
But, as a symbol of the decay of his country in its later years, few match Shevchenko. And he understood what lay ahead. In June 1987, when Mikhail Gorbachev was at the height of his powers, Shevchenko told an interviewer that the Soviet leader then beguiling the West was "a transitional figure, because he still believes his glasnost is compatible with a Leninist Socialist society. It is not. What will be the political shape of Russia in the next century I cannot judge, but Communism there as a system is doomed." Shevchenko expected collapse might take a generation. It happened within four years.
Arkady Nikolayevich Shevchenko, diplomat: born Gorlovka, Ukraine 11 October 1930; three times married (one son, one daughter); died Bethesda, Maryland 28 February 1998.