The extraordinary public rebuke by the United States’ closest surveillance partner has revealed an emerging characteristic of Donald Trump’s White House: a willingness to antagonize even its allies instead of admitting error. GCHQ, the UK surveillanceance mammoth intimately linked to the National Security Agency (NSA), has taken public exception to an allegation repeated from the White House podium that, if true, would probably shatter the Five Eyes intelligence alliance so dear to both Washington and London. Sean Spicer, the White House press secretary, credulously repeated on Thursday an account by a Fox News pundit, Andrew Napolitano, that GCHQ laundered surveillance on Trump at the behest of Barack Obama. Napolitano, who is in no position to actually know, made the allegation apparently to explain away the emerging consensus, even from senior Republicans on the intelligence committees, that there is no basis to Trump’s claim that Obama ordered that surveillance. GCHQ practically never responds to stories about its operations. But the implications of this one are severe. There would be no way for the NSA and GCHQ, which are joined at the hip, to continue their partnership if GCHQ was willing to interfere in the US political process. On Friday, 10 Downing Street said it had received assurances from the White House that it will not repeat the allegation, which suggests that the White House did not realize the implications of what it said. The context matters here. Spicer repeated Napolitano’s allegation for the same reason Napolitano made it: to defend Trump’s evidence-free assertion, on 4 March, that Obama had Trump’s team placed under surveillance.