Candid reflections of an ambassador
He is the United States Ambassador to the Court of St James. In days gone by, such envoys were described as "extraordinary and plenipotentiary". Five post holders went on to serve as president.
Yet Matthew Barzun appears to carry that weight of history with remarkable lightness. An internet pioneer, a moderniser, he was a key fund-raiser for President Obama. Before London, he was the US Ambassador to Sweden.
Today I had the chance to meet him during his first full visit to Scotland. His tour coincides with a series of challenges in US diplomacy and Scottish/American relations.
As we talk in Edinburgh, the US Senate intelligence committee is investigating complaints that America's National Security Agency tapped the communications of allies, including German Chancellor Angela Merkel.
The issue has provoked anger abroad - and contention back in the US. The ambassador stresses the president's determination to review intelligence gathering procedures.
And the Scottish challenge? The imminent 25th anniversary of the Lockerbie bombing. Ambassador Barzun reflects candidly that there persists anger in the US over the release of the sole convict, Abdelbaset al-Megrahi.
But he takes pains to emphasise that this lingering anger is trumped by close relations in other fields: in business, in education, in tourism. Scotland and the USA, he says, will "get through this".