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.

Peter Mandelson has been a pivotal figure in shaping modern British politics, but his Machiavellian tactics and questionable choice in friends have courted controversy, earning him the nickname, the "Prince of Darkness".