LONDON (Reuters)

Britain named Labour Party grandee Peter Mandelson as its ambassador to the United States on Friday, seeking to woo Donald Trump’s administration, avoid a trade war and ensure the two countries remain aligned on support for Ukraine.

A former European commissioner for trade and a key figure in Labour’s success under former leaders Tony Blair and Gordon Brown, Mandelson will become the first political appointee to the role in almost half a century.

The selection marks one of Keir Starmer’s most significant foreign policy moves since he came became prime minister in July, given the potential shocks that could reverberate from Trump’s return to power.

Starmer said the 71-year-old would become London’s man in Washington from January, replacing the highly-regarded Karen Pierce – a career diplomat drawn from the politically neutral civil service who is at the end of her term.

Rather than retaining Pierce, Starmer has opted to send a seasoned politician to Washington whose reputation as a charming but ruthless behind-the-scenes operator earned him the nickname “Prince of Darkness” in the British media.

Mandelson’s job will be to argue that Ukraine should be given all the support it needs in its war with Russia and that, as a close ally of the U.S., Britain should be spared any trade tariffs that Trump may impose once in power.

He will also need to be wary of Trump’s well-advertised relationship with Nigel Farage, the populist politician who championed Britain’s departure from the European Union and is a vocal critic of Starmer’s government.

The appointment is not without risk as Mandelson is no stranger to generating headlines: he was twice fired as a minister over separate scandals, and his belief in closer ties with China and opposition to Brexit may be at odds with Trump’s outlook.

The fate of a previous British ambassador to Washington – Kim Darroch – may also serve as a warning for Mandelson.

Darroch was forced to quit during Trump’s first term when leaked confidential memos showed he had called the then-president’s administration inept, earning the wrath of Trump, who called him stupid.

Mandelson has previously said that Britain must navigate a path between the U.S. and the European Union but does not need to choose one over the other.

“We have got to find a way to have our cake and eat it,” he told a Times podcast this year.