Four British men have successfully completed a controversial high-speed expedition on Mount Everest, reaching the summit in just five days with help from xenon gas. The climbers—who are all former special forces soldiers—left the United Kingdom on May 16.

Sherpa guide Kami Rita Sherpa broke a record he set for most summits of Mount Everest by completing his 31st climb on Tuesday.

A group of British men went from London to the summit of Everest and back in less than a week with the help of xenon gas. Mountaineers and the Nepalese government weren’t pleased.