Sir Kim Darroch has been made Britain's ambassador to Washington following his appointment in August.
He takes over the position from Sir Peter Westmacott, who is retiring from the diplomatic service.
Sir Kim has previously served as a national security adviser to David Cameron and was involved in efforts to secure compensation for the victims of IRA terrorism from the Gaddafi regime which funded them.
He has tweeted a photograph taken Thursday with president Barack Obama to mark the start of his duties, and sadly, compared to the POTUS, he seems a little awkward.
A good start to relations then!