In her decision as to whether to go ahead with the Chinese-backed Hinkley C nuclear power station – postponed from July apparently because of security concerns – Theresa May will find no better guidance than the advice which has been given to her and her aides while attending the G20 summit in Hangzhou this week. They have reportedly been advised to not to take their mobile phones, and to use temporary replacements while in China. They have also been given temporary email accounts which can be deleted upon return, and to avoid using public charging points for laptops and iPads. Any mobile phones that are taken to China, reports the Sunday Times today, should be concealed in security boxes out of fears that the Chinese security services have developed ways of accessing phones even when they are switched off.

If these are genuine concerns, and not the inventions of paranoiac inside MI6 or GCHQ, then they do seem to provide an answer to the Hinkley question: how can Britain possibly trust another country with it nuclear power infrastructure when we can’t trust it not to spy on government aides attending an international summit? Of course we want to encourage trade with China – we want to do business there and for the Chinese to invest here. But to allow involvement in sensitive nuclear power infrastructure seems an odd place to start.