He is a little-known figure until the testimony of November 5.
"Despite his unquestioned status as a close and senior advisor to the President, and the longstanding bipartisan position of that branch regarding the compelled congressional testimony of such advisors, the House Defendants threaten to hold Mr. Mulvaney in contempt or otherwise take adverse action against him for obeying the directive of the head of his branch", Mulvaney wrote in his motion. The videotape is an open and comfortable portrait of a wealthy family, and he is looking forward to living in Europe.
His background echoes the president's choice of his echo: a hotel operator and businessman with a millionaire turned his attention to politics.
He had originally backed a Trump rival in the 2016 presidential race - Jeb Bush.
Trump said he was releasing the transcript to be more transparent, then repeated his complaint about the House inquiry.
But, when Donald Trump was elected, Mr Sondland donated $1m (£781,000) to his inaugural committee.
His political patch extended to Ukraine, and he split much of his time between Brussels and Kyiv.
Mr. Sunderland called it a "special task".
Trump is accused of pressuring Ukraine President Volodymyr Zelenskyy to launch investigations for damaging information on former US Vice President Joe Biden, a leading candidate for the 2020 Democratic presidential nomination.
Hunter Biden is a board member of the Ukrainian Energy Corporation.
But Sondland also has testified that Trump told him personally that there was no quid pro quo.
For Gordon Sondland, his sudden declaration has caused incredulity, and endless comic material on USA prime-time TV networks. "It really made the old face look new". But Mr. Sondland said he and career State Department officials were unable to do anything about Mr. Giuliani. Impressions range from outward dislike of his style to open admiration.
They agreed to speak frankly in an anonymous situation.
"Of course he is an alienation expert". He didn't come from this diplomatic world, he didn't know, and he didn't seem to want to know. As you said, everyone drinks tea. "Maybe a Lapsang Souchong....it can leave a bitter taste".
One ambassadorial adviser who has spent decades in Brussels had kinder words. "He is aggressive and good at fighting, and some people may say high-lipoprotein".
But Giuliani has also withdrawn from his prominent public role as a defender of the President in the media after he himself came under scrutiny for his efforts to shape USA policy toward Ukraine. I know his position and respect it.
The official on-the-record view offers a different take. Mina Andreeva is the chief spokesman of the European Commission, he said: "We have been very professional in his life".
Diplomacy is the most diplomatic.
Ambassador Sondland and his team in Brussels were ed for comment this week, but were unavailable.
" Not long ago, we gave an introduction to the US Ambassador to Germany. "And you'll tell me if you think there's anything wrong with it".