Four British climbers pose on the summit of Mount Everest less than a week after leaving London, in one of the fastest ascents on record of the world's highest peak, in Nepal (Sandro Gromen via AP)

By Gopal Sharma KATHMANDU (Reuters) -Four British climbers became the first to scale Mount Everest on Wednesday using Xenon gas, which helped them save several weeks that mountaineers need to get used to high altitudes,