Around midnight on May 9th, 1996, 30 climbers left Camp Four on Mount Everest, and began trudging upwards towards the summit, writes John G O'Dwyer.
Fourteen of them were clients of two commercial expeditions aiming to put people who normally would get nowhere near an 8,000-metre mountain on to the roof of the world. For the privilege of a fully escorted ascent with bottled oxygen provided, the clients were happy to pay extravagantly.
First to leave were the New Zealand-based Adventure Consultants, led by Rob Hall and consisting of three mountain guides, six Sherpas and eight paying clients. Soon afterwards the American Mountain Madness team, led by Scott Fischer, with three guides, six Sherpas and six clients, began ascending.
Now there are two facts that every mountain leader knows. First, a group moves at the pace of the slowest member. Second, the larger the team the more unwieldy it becomes. And so, with large numbers and widely varying climbing abilities, inevitable bottlenecks occurred on the difficult sections such as the Hillary Step. It was 4pm before the last climber reached the summit - two hours beyond the latest time allowing for a descent before nightfall. Darkness enveloped the climbers and, as their oxygen supplies ran out, they were hit by a ferocious storm. Soon afterwards, like cars without fuel, many could move no further. In the end, seven expedition members, including Hall and Fischer, died in Everest's most lethal misadventure.
This tragedy seemed likely to end the practice of ordinary people paying extraordinary sums to climb Everest. Instead, the opposite has happened. Ten years on, demand has grown hugely, and the paradox of climbing is underlined once again. Unlike most other activities, a mountain tragedy and its attendant publicity actually increases the number of would-be participants.
And so each spring in Tibet and Nepal, two inhospitable and normally deserted glacier moraines sprout an array of colourful tents and are transformed into Everest base camps. Weather patterns on Everest ensure that all climbers with summit intentions arrive almost simultaneously. For most of the year the mountain is buffeted by hurricane-force winds. Each May, however, the approaching monsoon pushes the jet stream northwards over Tibet and allows a window of benign weather.
So climbing teams arrive in late March, acclimatise in April and aspire to reach the top in May.
At base camp there are two distinct groups. First, there are the constantly diminishing numbers of highly experienced climbers, who have served long mountain apprenticeships.
Generally, they rope together when climbing, with every team member taking responsibility for the safety of the others.
They eschew the easiest trail to the summit, with some referring to this as the "Yak Route".
Instead, they search for new challenges or attempt to replicate difficult routes previously completed.
The reward they seek is peer-group respect for pushing back the frontiers of the possible for other mountaineers.
The second group are mostly clients of commercial expeditions for whom the prestige of a summit photograph is worth almost any price.
Their struggles are not mountaineering ones but are personal by nature, since a hand-held ascent wins no prestige in the insular world of climbing.
As they are not considered self-reliant, Sherpas ascend the mountain in advance and place safeguarding ropes on any section that might be considered even remotely dangerous.
When the big day - or rather, big midnight - arrives, they clip to fixed ropes and trudge summitwards in darkness behind a professional guide. Success will depend on fitness, ability to acclimatise and luck with the weather. But it also requires determination in bucketfuls. Even on commercial expeditions, only the teak-tough can cope with the considerable risk and long drawn-out torture on the trail to the summit.
There are many who question if it was for this that Edmund Hillary blazed a trail in 1953. Even the great man himself had doubts and suggested that commercial expeditions engender disrespect for Everest. Others who have criticised the commercialisation include renowned Austrian climber Kurt Diemberger and Doug Scott, the first British summiteer.
Still, it is likely that the image of Everest will increasingly change from the ultimate mountaineer's mountain into the world's highest tourist attraction.
Purists will decry this trend as increasing environmental damage, threatening the integrity of local cultures and worsening the already serious rubbish problem on the mountainside. But few Nepalese will echo such sentiments.
The influx of climbers brings badly needed hard currency, provides considerable employment along the Everest trail and allows high-altitude Sherpas - on whom the success of every commercial expeditions depends - an otherwise impossible standard of living.