LONDON // Growing suspicion that militants blew up the Russian passenger jet above the Sinai desert on Sunday, killing all 224 on board, clouded talks between Egypt’s president Abdel Fattah El Sisi and the British prime minister David Cameron in London on Thursday.As Britain banned all flights to the Egyptian resort of Sharm El Sheikh, from where the Metrojet Airbus began its doomed journey, the fate of the aircraft dominated the agenda at the Downing Street meeting.