The Chinese are anxious that nothing should disrupt the high point of the run-up to the Beijing Olympic Games in August - the carrying of the Olympic Torch up Everest's slopes as part of its relay procession around the globe, due to take place sometime in the first half of May.
To make sure that nothing does disrupt it, the Chinese closed the mountain's north side in Chinese-occupied Tibet last week. At the weekend came the news that they have persuaded Nepal to close it from the south side also.
The closures are likely to last for about the first 10 days in May, but this is the absolutely crucial time for Everest expeditions seeking the necessary acclimatisation on the mountain's lower slopes - and it means that most if not all expeditions will be impossible. Among the many disappointed climbers will be the veteran British explorer Sir Ranulph Fiennes, who had hoped to make up for a failure to scale the peak in 2004.
Taking the torch up Everest is likely to prove a publicity coup for China on the grandest international scale. But the current nationalist unrest in Tibet, which led to violent protests in the capital, Lhasa, on Friday, is making the Beijing authorities extremely nervous.
Their anxiety is heightened by the fact that campaigns by Tibetan-independence activists have historically been supported by many climbers and mountaineers. Four American pro-Tibet demonstrators made their way to Everest base camp on the Tibetan side last year and unfurled a banner reading "One World, One Dream, Free Tibet 2008".
China announced the ban on climbing Everest from the Tibetan side on Wednesday in a letter to expedition companies from the China Tibet Mountaineering Association which said: "Concern over climbing activities, crowded climbing routes and increasing environmental pressures will cause potential safety problems in Qomolangma [Everest] areas. We are not able to accept your expedition, so please postpone your climbing."
News of the ban from the southern, Nepalese side came in an announcement from the Nepalese Tourism minister Prithvi Subba Gurung, who said that the closure was in response to a request from China, adding: "This is to prevent some people who could infiltrate and cause trouble during the time when they take the torch to the top."
The ban has thrown the climbing industry into turmoil. Sir Ranulph, for example, had been set make an attempt at scaling the summit on 15 May. However, the closure will leave no time for his expedition to fix ropes, cache oxygen and acclimatise. The 64-year-old had engaged the aid of the mountain guide and experienced Everest climber Kenton Cool, who had planned to take Sir Ranulph to the Alps in preparation for the Himalyan ascent. "With the mountain completely shut until 10 May our chances of a summit attempt are virtually zero," said Mr Cool. "Hopefully there is still room for negotiation with the authorities. We would only need a few days to stock camps and prepare, so we could still be in with a chance."
Beijing's Vice Mayor, Liu Jingming, who is overseeing Olympic preparations, said: "The torch relay to Mount Everest is a highlight of the whole relay and represents the idea of green Olympics, hi-tech Olympics and people's Olympics."
However, Mr Cool said that the Olympic Games were about competition and the celebration of sporting achievements, adding: "I don't see how closing the world's highest mountain to everyone but yourself is in the spirit of the games."
This year's Olympic Torch relay will begin on 25 March at Olympia, the ancient site of the games in Greece. From there it will travel to Athens and then to Beijing, arriving on 31 March. From Beijing, the torch will be carried by 21,880 torchbearers on a route passing through every continent except Antarctica before returning to China.
- Michael McCarthy and Jack Geldard