It was not John Bierman's idea to write this biography. When it was suggested to him, after the success of his last book, Alamein: war without hate (2002), he was initially reluctant, worrying that it might appear "less a genuine biography than a ride on the coat-tails of The English Patient". Few people, it is true, would be interested in reading about a long- forgotten Hungarian explorer were it not for the book and film. Yet this is a shame, because Laszlo Almasy was an interesting and important figure in his own right.

Born the second son of an untitled Hungarian aristocrat, Almasy was past 30 when he arrived in Egypt. After fighting with distinction in the First World War (in the cavalry and then as a pilot), he whittled away the turbulent postwar period before joining the Steyr Automobile Company as a driver-cum-mechanic. Arriving in Egypt as Steyr's representative, he embarked on pioneering test drives, and soon made his way into the vast, inhospitable tract of the eastern Sahara commonly known as the Western Desert.

Around the same time, he also became increasingly obsessed by two desert legends: Zerzura, the Atlantis of the desert; and the lost army of the great Syrian lead-er Cambyses which had, according to Herodotus, been engulfed by a giant sandstorm. Unravelling these two mysteries became his life's mission.

He was not alone; there were other explorers in the "Zerzura Club". Most were British - men such as Ralph Bagnold and Pat Clayton, who would go on to found the Long Range Desert Group. Almasy knew and travelled with both, having by then made a name for himself by rediscovering a lost stretch of an ancient route known as the Forty Days' Road. On one trip in 1932, he travelled with Robert Clayton-East-Clayton, who had arrived in Egypt with his beautiful wife, Dorothy, and a Havilland Gipsy Moth named Rupert. Although the couple were undoubtedly the inspiration for the Cliftons in Michael Ondaatje's novel, Dorothy took an immediate dislike to the bisexual Almasy.

Almasy's single greatest achievement was the discovery of a number of Stone Age rock paintings in caves along the southern edge of the huge Gilf Kebir plateau. However, he was also a pioneer of motorised desert travel. Bierman offers vivid descriptions of the rigours and hardships in the 1930s of traversing the Western Desert, which even today is a forbidding and dangerous place.

In the wake of The English Patient, a flurry of articles appeared claiming that Almasy had spied for Italy in the 1930s and that he became a Nazi during the Second World War. Bierman is careful not to come down definitively on either side, but I remained unconvinced that Almasy was either. His whole purpose in life was his quest for Zerzura and Cambyses's army; he appears to have had little interest in politics. It is true that he ingratiated himself with the Italians while replenishing stocks at one of their outposts, but he also supplied the British with information while in Cairo. His motive on both occasions was simply to make life easier for himself. Almasy was certainly never discreet. And yes, he did work for the Abwehr during the war. But again, this seems to have been purely for the purpose of getting back to Egypt. There is convincing evidence to suggest that, later in the war, he helped save two Hungarian Jews from being deported to the death camps.

Although Bierman has dedicated his fascinating book to Bagnold and the men of the Long Range Desert Group, you cannot help feeling that even he warmed to this strange loner of a man. Let us hope that his efforts go some way to restoring Almasy's reputation as an explorer.

James Holland's novel The Burning Blue is out in paperback from Arrow