Lord Mandelson - set to be the UK's ambassador to the US - revels in his image as a behind-the-scenes fixer.

Dan Mullaney, a former assistant U.S. trade representative under Trump and other presidents, who crossed paths with Mandelson in Brussels, agreed with his analysis that the U.K. would not necessarily need to choose between closer ties with Washington or Brussels.

Britain named Labour Party grandee Peter Mandelson as its ambassador to the United States on Friday, seeking to woo Donald Trump's administration, avoid a trade war and ensure the countries remain aligned over Ukraine.