After mysteriously falling from a London balcony, Ashraf Marwan was found to be halfway through an expose of his life

AN Egyptian millionaire who mysteriously fell to his death from the balcony of his London flat after being named as a Mossad spy was writing a book that threatened to expose the murky world of Arab-Israeli espionage.

Ashraf Marwan, the son-in-law of the late President Gamal Abdel Nasser of Egypt, was more than halfway through a book about the 1973 Yom Kippur war - in which he is alleged to have played a key intelligence role - when his body was discovered last week.

Marwan's death, which police are treating as "unexplained", has sent ripples across the Middle East and shocked some of Britain's wealthiest people.

The 62-year-old financier was a former shareholder of Chelsea football club and counted Ken Bates, its former chairman, Adnan Khashoggi, the Saudi arms dealer, and Tiny Rowland, the late business tycoon, among his acquaintances.

But it was Marwan's espionage activities that have surrounded his death with intrigue. Israeli intelligence sources claimed this weekend that he had been one of the greatest spies recruited by Mossad.

They said Marwan had supplied the Israeli secret service with a treasure trove of information, including the secret plans drawn up by Egypt's leaders to cross the Suez Canal and attack Israel in 1973.

Ahron Bregman, an Israeli historian at King's College London, however, believes Marwan was a double agent who misled the Israelis over Egypt's plans for the war. This weekend Bregman said the Egyptian had left three messages on his answerphone last Tuesday, urgently asking him to make contact.

"I was out, but eventually spoke to him at around 4pm," said Bregman. "He asked me about the recent libel case in Israel."

The case involved two former Israeli intelligence officers, one of whom had accused the other of leaking Marwan's name as a spy. Bregman said Marwan had described the court case as "a headache" and asked to meet him at King's College the following day.

"It was very clear that we were going to meet, but there was no call on Wednesday and I heard later in the day that he had died," said Bregman, who claimed in an Egyptian newspaper article in 2003 that Marwan had been a double agent. "He told me never to send anything to his address because it was watched. He was always very cautious and never referred to himself by name."

Marwan fell four floors to his death from his flat at Carlton House Terrace overlooking St James's Park. Police are exploring three possibilities: that he was murdered, that he jumped - although no suicide note has been found - or that he fell.

One possibility is that Marwan was taking medicinal drugs that made him faint. He had had three heart operations, according to a friend, Marwan, lived with his wife at the London flat where he died, was writing about the Yom Kippur war, in which he may have played a key intelligence role, and "had been very unwell".

Other friends believe that he feared being assassinated after being "outed" as a Mossad spy.

The son of an Egyptian general, Marwan studied at Cairo university where he met Mona, Nasser's daughter. He was 21 and she was 17. The couple married a year later and went on to have two sons, Gamal and Ahmed.

Marwan was soon leading a double life. In 1969, according to Israeli sources, he slipped into the Israeli embassy in London and - before being ejected - told a security guard: "Send my name to Tel Aviv. They'll know who I am. I'll be back in a week's time."

A week later one of Mossad's most senior controllers - known by the initial D - flew to Britain and lavished five-star hospitality on Marwan. It was the start of a 30-year relationship that saw highly classified information, including the minutes of meetings between Anwar Sadat, the Egyptian president, and other world leaders regularly passing into Mossad's hands.

"It's as if we were sleeping in the bedroom of the Egyptian presidential couple," recalled an Israeli source.

Marwan, who worked in Sadat's office, made only two conditions in return for his services: he was to be paid £50,000 for each significant meeting he had with his Israeli handlers and he insisted that D was to be his sole controller.

Before long Marwan's raw intelligence became essential reading for Golda Meir, the Israeli prime minister, and Moshe Dayan, her defence minister. "When information arrived from Marwan it was sent directly to the leaders," said an insider. "It was better than any John le Carré espionage thriller."

By 1972 Marwan was a millionaire and had revealed details to Mossad about secret arms deals between Egypt and the Soviet Union, according to Israeli sources.

But the best was yet to come. Marwan invited D to a meeting in London at which he handed his controller a suitcase full of documents outlining Egypt's plans to cross Suez and attack Israel. Intelligence sources claim that overconfident Israeli military chiefs ignored the plans and they were left to sit in a safe in Tel Aviv.

In September 1973 King Hussein of Jordan tipped off Meir that Syria was also about to launch an attack. Meir sought Marwan's advice.

But Marwan could not be reached. Finally, only 24 hours before the outbreak of war, a message was intercepted in the Mossad HQ in Tel Aviv: "Meet me tomorrow in London."

Marwan managed to leave Sadat's side by convincing the Egyptian president that he should travel to Libya to warn Colonel Gadaffi about the imminent conflict. From Tripoli, he flew to Malta and on to London.

Mossad stopped El-Al's last flight to London as it prepared for take-off. The Boeing 707 waited on the tarmac for more than 30 minutes. Passengers saw a car speeding towards the aircraft and two fair-haired men climbed in. They were Zvi Zamir, the head of Mossad, and D, Marwan's controller.

According to Israeli sources, Zamir rang Tel Aviv in the early hours of the morning and told colleagues: "Call Golda [Meir]. It's today at 6pm, both Syria and Egypt."

Marwan's tardiness raised suspicions that he was a double agent but he was exonerated by Mossad. In Egypt Marwan remained a hero and was decorated by Sadat before moving to London, where he became active in the business world.

Meanwhile, in Tel Aviv, Marwan's former controller, D, received the news of his death with sadness. With Marwan's book unfinished, perhaps the motives for his secret life will never be fully explained.