Trump team asked which EU state is next to exit

In a candid last farewell interview with reporters ahead of his departure on 20 January, the diplomat described the Trump call as a "misperception" of the Union's future, disseminated by former Ukip leader Nigel Farage.

Farage, a British MEP who has long campaigned for the demise of the European Union, has had privileged access to the US president-elect.

He now wants to meet with Gardner but the outgoing ambassador, a self-described defender of the EU, remains ambivalent.

"I got a letter from Nigel Farage, which is rather interesting. He knows I'm leaving and he knows my views are the absolute polar opposite of everything he has said."

Gardner said Farage had referred to him in the letter as "your excellency" a half dozen times.

"I take huge exceptions to some things he's done and I will tell him," said Gardner.

The American ambassador said he would soon be "unshackled" from the "bureaucratic restrictions of the job" and aims to speak out in defence of the US and EU relations.

The two men have never met.

But the mood at the US embassy appears wary ahead of Gardner's future replacement. Speculation is rife on who will take on the job.

Staff working at the mission, non-career diplomats, have all been unceremoniously told to vacate the premises by 20 January.

Gardner described the Trump demand as a "breach of precedent" because missions are usually allowed to take weeks or even months to clear out. He was given notice on 23 December.

Some have struggled to find new housing after receiving notice of their imminent departure via a telegram.

"I didn't particularly want to stay any more than necessary because my views are not the views of those coming in. But for some, it has had a real human impact," he said.

He also warned against his future replacement of becoming the "cheerleader" for Brexit and noted that access to Europe's single market was strategically vital to both US and EU business interests.

He said any move by Trump or his team to support the break up of the Union would be "shear folly".

"It's lunacy and I would think it would be a widely shared view."

He also advised Germany's chancellor Angela Merkel to warn the incoming US embassy replacement team in Brussels against "splitting the EU, one member state to another."

He said Germany, along with the EU institutions, are now shouldering the "weight of history" to defend democracy, human rights, and "values that guided a transatlantic partnership for decades."

In terms of policy work, Gardner said his biggest regret was not being able to finalise the TTIP, the US and EU free trade agreement.

But he noted significant improvements have been made on policies dealing with data and that trust, broadly lost following the US snooping revelations of Europeans, has improved between the two sides.

"It's been great, it's been great. Best job," he said.