“China’s main secure command centre is in the Western Hills, north-east of the new facility, and was built decades ago at the height of the Cold War,” the former official said. “The size, scale and partially buried characteristics of the new facility suggest it will replace the Western Hills complex as the primary wartime command facility.

China has made little secret of its expansionist ambitions, in particular its insistence that the autonomous island of Taiwan is part of its territory.

China’s military is building a massive complex in western Beijing that US intelligence believes will serve as a wartime command centre far larger than the Pentagon, according to current and former American officials.