LONDON — Christian Turner has been chosen as Britain’s new ambassador to the United States.

The U.K. government on Thursday picked the career diplomat — who had been due to become Britain’s designated representative to the United Nations in the coming months — to take on the key transatlantic diplomacy role vacated by Peter Mandelson, amid controversy over Mandelson’s friendship with convicted sex offender Jeffrey Epstein.

The PM’s business adviser Varun Chandra had been seen as the frontrunner as recently as this week, but Turner secured the plum job after Keir Starmer was persuaded to appoint from within the Foreign Office.

One Foreign, Commonwealth and Development Office (FCDO) official familiar with the final shortlist process said there had been a “massive fightback in the past days” to sway the PM towards appointing a career diplomat.

Turner has spent three years as political director at the Foreign Office in London, but brings U.S. experience too. He spent four years in Washington from 2002 to 2006 as first secretary at the British Embassy there.

The decision to opt for an FCDO veteran comes at a crucial time for U.S and European relations. President Donald Trump is pushing for peace in Ukraine — and has been aiming pointed attacks at Europe’s leaders he sees as weak. U.K. and U.S. negotiators are continuing to haggle over key elements of a trade deal unveiled in May.

Turner was U.K. deputy national security adviser to Theresa May as prime minister.

This developing story is being updated.