It might only be a small paper sign, but the name it bears links to a mysterious figure whose fortune runs into the billions. Nearly two dozen floors up an anonymous Bangkok tower, this is the registered address of Nigel Farage ’s crypto backer Christopher Harborne. But the controversial tycoon is not here and neither are his staff when we visit – we are told “messengers” sometimes arrive to pick up mail. The only real clue of his presence is the sign, among a series of other firms on the wall,