Sir Philip Barton, the British high commissioner to India for a matter of weeks, has been appointed by Downing Street to head the newly merged Foreign, Commonwealth and Development Office. As permanent undersecretary of the department from next month, he will play a critical role in preparing the post-Brexit “global Britain” policy. The lightning promotion to run the newly merged department indicates the degree of haste with which decisions are being taken in Whitehall. Barton had only just started to make public appearances in India after promising to be a bridge between India and the UK. He was previously director general responsible for the UK government’s long-term strategic response to the coronavirus outbreak. He is in effect taking over from the current Foreign and Commonwealth Office (FCO) permanent undersecretary, Sir Simon McDonald, who is standing down as part of a widespread changing of the guard at the top of Whitehall. The cabinet secretary, Sir Mark Sedwill, is also retiring, as is the head of MI6, Alex Younger, who is being replaced by the political director at the Foreign Office, Richard Moore. Barton faces the task of pressing ahead with the merger of the FCO and Department for International Development (DfID), which is due to be completed by the end of September. The process will involve reforming departmental salary structures and deciding new lines of accountability between the old DfID staff in the field and the local diplomatic network. Many DfID staff fear their poverty reduction work will be undermined by a diplomatic staff determined to put UK commercial interests first. Barton will face the continuing consequences of leaving the EU, requiring the Foreign Office to move resources towards bilateral relations in individual European capitals, and away from Brussels. He will also need to manage the consequences of a November presidential election in the US, which may not have a direct impact on future relations with China but could require a UK review of its relations with Russia and in the Middle East. Barton was acting chairman of the joint intelligence committee from 2016 to 2017. He has also worked in the Cabinet Office as director general on the 2016 anti-corruption summit hosted by the then prime minister, David Cameron, and director of foreign policy and Afghanistan/Pakistan coordinator supporting the National Security Council. He was private secretary to the prime ministers John Major and Tony Blair. His appointment as high commissioner to India was announced on 6 February. He arrived in Delhi on 12 June before completing his quarantine on 26 June and presenting his credentials to the Indian president on 8 July. As director general consular and security, he had last summer been acting permanent secretary at the FCO during McDonald’s summer break.