Both valued at pounds 13m, they were swapped on the tarmac at Vienna airport in July. Mr Hoare discussed the hair-raising difficulties of the deal with the Independent last week, the first time he has publically admitted his involvement.
The De Kooning belonged to the Iranian government and arrived from Tehran in President Ali Akbar Rafsanjani's private jet. Mr Hoare, who had purchased the manuscript from the estate of an American millionaire, Arthur Houghton II, the day before the exchange, had it flown first to Paris for inspection by Iranian experts and then on to Vienna. The exchange took place in a van beside the jet and the manuscript - which is regarded by some as the greatest work of art ever created in Iran but was banned for many years after the revolution in 1979 - returned home through the afternoon sky.
Oliver Hoare, 49, has not previously told the story of his coup. 'I didn't want to talk to anyone,' he explained. 'I could just see the headline - Di's Pal in Trading Deal with Revolutionary Government.' It was revealed in August that Mr Hoare had been plagued by anonymous telephone calls traced to the Princess's private line at Kensington Palace.
The manuscript, the Houghton Shahnameh - Epic of the Kings - was bought in 1959 by Houghton, an industrialist whose family founded Corning Glass. The Shahnameh, is an epic poem composed by Firdowsi in the 10th century; it recounts the legends and historical traditions of ancient Iran.
The Houghton manuscript is the richest ever created. It originally contained 258 paintings, 759 illuminated pages of text, a brilliant illuminated rosette and a 16th-century binding; it is now down to 118 paintings but the rest remains intact. It was begun at the behest of Shah Isma'il, the founder of the Persian Safavid dynasty around 1522, as a gift for his young son and successor, Shah Tamasp. The vast undertaking, which took more than two decades to complete, was continued by Tamasp. All the greatest artists of the golden age of Persian painting contributed to the manuscript.
Mr Houghton's break up and dispersal of the manuscript is widely regarded as one of the most significant acts of artistic vandalism of the post-war years. In 1972 he gave 78 of the paintings to the Metropolitan Museum in New York as a tax-deductible gift. He sold seven pages at Christie's in 1976 for pounds 785,000; one of the paintings made pounds 308,000, which is still the record auction price for a Persian miniature. Encouraged by this success Mr Houghton gave 40 or so pages to Agnew's, the Bond Street dealers, to sell on his behalf. Then, in 1988, he deposited the remaining manuscript with Lloyds Bank in London and asked Christie's to dispose of it. Christie's sold another 14 pages for pounds 976,800 before Mr Houghton's death in April 1990.
It was at this point that Mr Hoare came into the picture. The manuscript had been left to a trust with instructions that it should be sold for the benefit of his widow. Mr Houghton's son, Arthur Houghton III, was determined from the start that it should not be dispersed piecemeal.
He visited all London's Islamic dealers and art auctioneers asking for ideas on how the manuscript should be sold. Mr Hoare's first idea was to raise money from Iranian exiles living in the United States to fund its purchase for the Metropolitan Museum. 'But fund raising isn't really my thing and it didn't work.'
Then he heard a rumour that Iran's new Cultural Heritage Organisation was interested in repatriating Iranian art treasures. He realised from the start that a pounds 13m art purchase would be politically unacceptable to the Iranian government and his first, carefully worded, letter to the director of the organisation suggested that Iran might pay with art.
'Since I'd heard at the time that the Museum of Contemporary Art was closed, I suggested that there might be things there that didn't fulfill a role in their cultural plans . . . They sent a scholar who lives in Paris to see me, Chahryar Adel, a very highly respected expert on Islamic paintings. He explained that the Shahnameh was number one of the list of things the Cultural Heritage Organisation wanted to get back. But it was politically immensely dangerous and the discussions in Iran went on for two years.'
It was only at the end of 1993 that agreement came through from Iran that they were prepared to accept a one-off transaction based on items owned by the Contemporary Art Museum which could never be exhibited in an Islamic republic - in other words, female nudes or paintings with an overtly erotic content.
The final deal was hammered out at a meeting in Paris last June.
The only mystery that now remains is where De Kooning's woman has gone. Mr Hoare lips are sealed - but he did indicate that a home was found for it before the deal was struck.
Meanwhile, the Tate is trying to borrow it for the De Kooning exhibition in February.
Contemporary Art Market returns next week.
(Photographs omitted)Reuse content