LONDON (Reuters) - British Prime Minister Theresa May appointed a senior career diplomat as envoy to the European Union to replace an ambassador who quit with a scathing resignation letter that exposed frustration among officials over her strategy.

Tim Barrow, political director of the Foreign and Commonwealth Office and a former ambassador to Moscow, would take up the post next week, May’s Downing Street office said, following the abrupt resignation of Ivan Rogers.

The selection of Barrow, a 30 year veteran diplomat, could disappoint some Brexit campaigners who would like to see a known eurosceptic in the post, but may reassure Britain’s cadre of civil servants that their expertise is still valued.

Barrow has served as first secretary at Britain’s embassy in Brussels but is not known to have taken a strong public position on Brexit.

In a statement released by May’s Downing Street office, Barrow said he looked forward to joining the new government department tasked with overseeing the exit from the European Union, “to ensure we get the right outcome for the United Kingdom as we leave the EU”.

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Downing Street described him as “a seasoned and tough negotiator, with extensive experience of securing UK objectives in Brussels”.

May intends to launch the two-year process of negotiating to leave the bloc by the end of March, beginning what is expected to be some of the most complicated international talks Britain has engaged in since World War Two.

She has so far said little publicly about Britain’s negotiating position, arguing that to do so would weaken London’s hand in talks.

Rogers said in a letter to his staff that May’s negotiating objectives were as yet unknown and told them: “I hope you will continue to challenge ill-founded arguments and muddled thinking”.

After Rogers’s resignation, some Conservative Party Eurosceptics said he should be replaced by someone who was more positive about Brexit.