This explanation was perfectly reasonable, but he was not satisfied with it. It did not wholly account for his sense of happiness – even of joy. Warren Kingsley, who was fond of diving, had often told him that he felt such an emotion in the weightless environment of the sea. Morgan had never shared it, but now he knew what it must be like. He seemed to have left all his cares down there on the planet hidden below the fading loops and traceries of the aurora.

The stars were coming back into their own, no longer challenged by the eerie intruder from the poles. Morgan began to search the zenith, not with any high expectations, wondering if the Tower was yet in sight. But he could make out only the first few metres, still lit by the faint auroral glow, of the narrow ribbon up which Spider was swiftly and smoothly climbing. That thin band upon which his own life – and seven others' – now depended was so uniform and featureless that it gave no hint of the capsule's speed; Morgan found it difficult to believe that it was flashing through the drive mechanism at more than two hundred kilometres an hour. And, with that thought, he was suddenly back in his childhood, and knew the source of his contentment.

He had quickly recovered from the loss of that first kite, and had graduated to larger and more elaborate models. Then, just before he had discovered Meccano and abandoned kites forever, he had experimented briefly with toy parachutes. Morgan liked to think that he had invented the idea himself, though he might well have come across it somewhere in his reading or viewing. The technique was so simple that generations of boys must have rediscovered it.

First he had whittled a thin strip of wood about five centimetres long, and fastened a couple of paper-clips on to it. Then he had hooked these around the kite-string, so that the little device could slide easily up and down. Next he had made a handkerchief-sized parachute of rice paper, with silk strings; a small square of cardboard served as payload. When he had fastened that square to the wooden strip by a rubber band – not too firmly – he was in business.

Blown by the wind, the little parachute would go sailing up the string, climbing the graceful catenary to the kite. Then Morgan would give a sharp tug, and the cardboard weight would slip out of the rubber band. The parachute would float away into the sky, while the wood-and-wire rider came swiftly back to his hand, in readiness for the next launch.

With what envy he had watched his flimsy creations drift effortlessly out to sea! Most of them fell back into the water before they had travelled even one kilometre, but sometimes a little parachute would still be bravely maintaining altitude when it vanished from sight. He liked to imagine that these lucky voyagers reached the enchanted islands of the Pacific; but though he had written his name and address on the cardboard squares he never received any reply.

Morgan could not help smiling at these long-forgotten memories, yet they explained so much. The dreams of childhood had been far surpassed by the reality of adult life; he had earned the right to his contentment.

“Coming up to three eighty,” said Kingsley. “How is the power level?”

“Beginning to drop – down to eighty-five percent – the battery's starting to fade.”

“Well, if it holds out for another twenty kilometres, it will have done its job. How do you feel?”

Morgan was tempted to answer with superlatives, but his natural caution dissuaded him. “I'm fine,” he said. “If we could guarantee a display like this for all our passengers, we wouldn't be able to handle the crowds.”

“Perhaps it could be arranged,” laughed Kingsley. “We could ask Monsoon Control to dump a few barrels of electrons in the right places. Not their usual line of business, but they're good at improvising. . . . aren't they?”

Morgan chuckled, but did not answer. His eyes were fixed on the instrument panel, where both power and rate of climb were now visibly dropping. But this was no cause for alarm; Spider had reached 385 kilometres out of the expected 400, and the booster battery still had some life in it.

At 390 kilometres Morgan started to cut back the rate of climb, until Spider crept more and more slowly upwards. Eventually the capsule was barely moving, and it finally came to rest just short of 405 kilometres.

“I'm dropping the battery,” Morgan reported. “Mind your heads.”

A good deal of thought had been given to recovering that heavy and expensive battery, but there had been no time to improvise a braking system that would let it slide safely back, like one of Morgan's kite-riders. And though a parachute had been available, it was feared that the shrouds might become entangled with the tape. Fortunately the impact area, just ten kilometres east of the earth terminus, lay in dense jungle. The wild life of Taprobane would have to take its chances, and Morgan was prepared to argue with the Department of Conservation later.

He turned the safety key and then pressed the red button that fired the explosive charges; Spider shook briefly as they detonated. Then he switched to the internal battery, slowly released the friction brakes, and again fed power into the drive motors.

The capsule started to climb on the last lap of its journey. But one glance at the instrument panel told Morgan that something was seriously wrong. Spider should have been rising at over two hundred klicks; it was doing less than one hundred, even at full power. No tests or calculations were necessary; Morgan's diagnosis was instant, for the figures spoke for themselves. Sick with frustration, he reported back to Earth.

“We're in trouble,” he said. “The charges blew – but the battery never dropped. Something's still holding it on.”

It was unnecessary, of course, to add that the mission must now be aborted. Everyone knew perfectly well that Spider could not possibly reach the base of the Tower carrying several hundred kilos of dead-weight.

Ambassador Rajasinghe needed little sleep these nights; it was as if a benevolent Nature was granting him the maximum use of his remaining years. And at a time like this, when the Taprobanean skies were blazing with their greatest wonder for centuries, who could have stayed abed?

How he wished that Paul Sarath was here to share the spectacle! He missed his old friend more than he would have thought possible; there was no-one who could annoy and stimulate him in the way that Paul had done – no-one with the same bond of shared experience stretching back to boyhood. Rajasinghe had never thought that he would outlive Paul, or would see the fantastic billion-ton stalactite of the Tower almost span the gulf between its orbital foundation and Taprobane, thirty-six thousand kilometres below. To the end Paul had been utterly opposed to the project; he had called it a Sword of Damocles, and had never ceased to predict its eventual plunge to earth. Yet even Paul had admitted that the Tower had already produced some benefits.

For perhaps the first time in history, the rest of the world actually knew that Taprobane existed, and was discovering its ancient culture. Yakkagala, with its brooding presence and its sinister legends, had attracted special attention; as a result, Paul had been able to get support for some of his cherished projects. The enigmatic personality of Yakkagala's creator had already given rise to numerous books and videodramas, and the son-et-lumiиre display at the foot of the Rock was invariably sold out. Shortly before his death Paul had remarked wryly that a minor Kalidasa industry was in the making, and it was becoming more and more difficult to distinguish fiction from reality.

Soon after midnight, when it was obvious that the auroral display had passed its climax, Rajasinghe had been carried back into his bedroom. As he always did when he had said goodnight to his household staff, he relaxed with a glass of hot toddy and switched on the late news summary. The only item that really interested him was the progress that Morgan was making; by this time he should be approaching the base of the Tower.