The employment of such tactics may sound dramatic but they are par for the course in an age of digital espionage and information security. For visits to China these precautions have been standard for at least a decade, such is the expectation that Beijing will eavesdrop and monitor. “The rest of the advice,” the senior security official said, “was warning middle-aged men that if an attractive young Chinese woman appeared interested in you, she probably wasn’t”. A former aide recalled that China insisted on supplying a personal protection officer “over six-and-a-half-foot tall” to follow the British prime minister and his team as closely as reasonably possible. The Lib Dem, who was then business secretary, was visiting China and did not have his mobile phone with him.