I signed up for diplomacy, but got politics and – honestly speaking – insurgency. I’m London’s insurgent diplomat. That’s not at all a complaint. I have always loved a good fight, particularly when I feel I’m on the right side of history, and on this I certainly am: as the representative for the interim President of Venezuela Juan Guaidó to the United Kingdom and Ireland, my mission is to bring both my host countries on board as reliable allies of the Venezuelan people, defending them from the predations of the Nicolás Maduro dictatorship. It’s a far cry from the more prosaic ambassadorial duties of promoting tourism, foreign investment or improving trade terms. I also have none of the bells and whistles of London ambassadors, not even a salary. As the New Year’s drinks party with the foreign secretary at Lancaster House wound down and my colleagues hopped into the back of their chauffeur-driven black Mercedes, I walked to Green Park tube. That’s likely one of the reasons the Financial...