Donald Trump joined Boris Johnson at a Downing Street reception for world leaders tonight to cap off the first full day of Nato’s 70th anniversary summit in London. The Prime Minister, who has been cautious to downplay his friendship with the President over fears his divisiveness could damage Conservative electoral prospects, did not greet his US counterpart on the steps of Number 10 for the traditional handshake. Instead, Mr Trump and his wife Melania posed in front of the famous black door together before heading inside to meet Mr Johnson who was waiting across the threshold. No bilateral meetings had been agreed between the White House and Downing Street prior to the summit, which comes in the middle of a crunch election campaign with less than two weeks until Britain goes to the polls. Conscious of how voters typically loathe meddling by foreign leaders in their elections, Mr Johnson has been hoping the notoriously brash and unpredictable President does not do, say or tweet anything that could sink his campaign. But today Mr Trump waded into an ongoing Tory-Labour row by pouring cold water on Jeremy Corbyn’s main campaign attack line which claims the US is eyeing up the NHS…