Chinese leader Xi Jinping has made a “deep mistake” with Beijing’s spy balloon saga, a former head of the UK’s Secret Intelligence Service says. Sir Alex Younger, the former head of Britain’s spy agency, told the BBC that China’s assumption of how the US would react to surveillance balloons being sent across its territory “wasn’t properly thought through”. He added that should US parts be found in the balloons, four of which have now been shot down, it would further encourage Washington DC to restrict China’s access to advanced technology. And he said the growing diplomatic and military crisis potentially...