THE JOURNEY TO THE TOP OF THE WORLD

THE PHOTOGRAPHS on these pages are a dramatic record of a bold adventure. On the third of April 1933, two small biplanes took off from an airfield in the north of India and raised human exploration to new heights; they flew for the first time over the summit of Mount Everest. In so doing, they gave the world a precious virgin view of a place untouched by a human foot. It would be another 20 years before Hillary and Tenzing clambered to this remote top, and stuck a flag in it.

These days, the ascent of Everest is almost routine. So it is hard to realise that the flight over the mountain was only the dramatic final step of a much longer journey. The planes left Heston aerodrome in Middlesex on 16 February; it took them three weeks to fly to India, with overnight stops all the way: Lyon, Naples, Sicily, Tripoli, Baghdad, Delhi - and all stations to Everest. The adventurers, led by Lord Clydesdale, were inspired by the dying pangs of imperial confidence - the desire to be the first, the highest, the bravest, and celebrate with champagne afterwards. They were certainly daring: on that first flight the camera failed, so on 19 April, "without authority from home", the pilots took their uninsured planes up once again. It was, reported the Times, "a magnificent act of insubordination".

The project was financed by the celebrated patriot Lady Houston, the queen of aeronautics who also funded the birth of the Spitfire. It would display, she felt, the vigorous pluck of the British to any doubting Indians. The pilots fitted the bill nicely - they prepared for the flight by shooting crocodiles. The Indians were impressed: village rumour had it that these British sky wizards were planning to fly round the Moon - an object hardly more remote.

With the passage of 50 years the pictures have acquired depth. In 1933 they possessed the simplest virtue of photography: they brought news from afar. Now, we have to work to drain Everest of familiarity - just as it is hard to equate so famous and resonant a title with that of the Surveyor General of India who gave his name to "Peak XV". The pictures do retain something of that freshness, that secret sense of an unvisited realm; we can still feel the weight of these first footprints in the sky. But seen today, they present us with a difficulty, since they are not in themselves remarkable, and have been superseded in beauty or vividness a thousand times. Now, they seem like images not so much of the mountain top as of the expedition that obtained them.

They record above all a landmark in aviation. And their resonance has more to do with the striking novelty of the angle of vision than with the appearance of Everest itself. The view is not, after all, so astonishing: the summit looks much like Mont Blanc, or Snowdon in winter: rock, ice, sky. It must have been reassuring to see that the roof of the world was so solid; but otherwise it looked as anyone might have expected: high, cold and uninhabited.

But these are, in effect, photographs of photography. This was one of the triumphant beginnings of a new way of seeing: the aerial view. If they shiver with romantic energy it is only partly because of their charming amateurishness - the fierce sunlight splashing into the frame, the dark smudges on the horizon, the blackness of the black, the whiteness of the white. Mainly it is down to the frail touches of hopeful human engineering in the foreground: the constant suggestion of struts, wires and flapping wing tips.

It is these touches of Biggles, more than the Himalayas, that inject drama into the pictures. The mountains have not changed, but these tipsy aircraft now seem like cartoon aeroplanes: they invite us to imagine freezing wind over leather goggles, an engine's roar in an untrodden space, the leaky hiss of an improvised oxygen mask, and the whump of a wooden propeller struggling to grip thin air.

They also throw into focus the extent to which we would, from this point on, begin to imagine ourselves in a new way - as seen from above. In the years that followed, this modern vantage point would inspire both a new love (of the panoramic view) and a new dread (of high-altitude bombing). But the plucky pilots wheeling exuberantly in the high winds above Nepal, dive-bombing elephants for a lark, hardly had time for such thoughts. It might have spoilt their fun had they wondered what potent seeds they were sowing. One was pressed almost into the side of Everest by a fierce downdraft; flying ice smashed his windscreen. Another found his legs being burnt by his electrically heated suit. He reached down and switched it off - and almost froze instead.

! A limited edition of 20 prints taken from the original negatives of the Houston Mount Everest Expedition is now available; call the Discovery Gallery on 0181 543 4238 for details. The photographs will be exhibited at the Royal Geographical Society later in the year.