Barton joined the
Foreign and Commonwealth Office (FCO) in 1986 and served at
Caracas,
New Delhi, at the FCO, and on secondment to the
Cabinet Office and as a private secretary to the
Prime Minister. He was deputy
High Commissioner to
Cyprus 2000–04; deputy Governor of
Gibraltar 2005–08 (with a spell as acting Governor in 2006); Director, South Asia, at the FCO 2008–09; Director, Foreign Policy and Afghanistan, and Pakistan Co-ordinator at the Cabinet Office 2009–11; deputy
head of mission at
Washington, D.C. 2011–14; and was appointed High Commissioner to
Pakistan from January 2014. Anti-tobacco movements in Pakistan and in the UK blamed Barton for his participation in a delegation led by
British American Tobacco in 2015 to complain about the Pakistani government's decision to increase the size of health warnings on cigarette packs. "Inside sources at the Health Ministry confirmed the participation of the British High Commissioner in the meeting as a member of the delegation." He left Islamabad at the end of his assignment on 11 February 2016 and took up a post as Director General Consular & Security at the Foreign & Commonwealth Office in London, which he left in January 2020 to assume the role of High Commissioner to India, with the presentation of his credentials to the
President of India on 8 July 2020. He was the shortest-serving High Commissioner to India on record. He departed this role and became the first
Permanent Under-Secretary of State for the newly combined Foreign, Commonwealth & Development Affairs Office and thus Head of
HM Diplomatic Service on 2 September 2020. He succeeded
Sir Simon McDonald who had served since 2015. In 2021, Sir Philip apologised for the treatment of gay staff: “The ban was in place because there was a perception that LGBT people were more susceptible than their straight counterparts to blackmail and, therefore, that they posed a security risk. Because of this misguided view, people’s careers were ended, cut short, or stopped before they could even begin. And the diplomatic service undoubtedly deprived itself of some of the UK’s brightest and best talent. I want to apologise publicly for the ban and the impact it had on our LGBT staff and their loved ones, both here in the UK and abroad.” In December 2021, he admitted failing to show leadership after he began a three-week holiday two days before the Foreign Office internally accepted Kabul was about to
fall to the Taliban. Sir Philip remained on holiday until 28 August. During questioning by the Foreign Affairs Select Committee, he admitted this was a mistake. In January 2024, he was criticised by the Chair of the
Foreign Affairs Select Committee,
Alicia Kearns, for being reticent to agree that
Israel has a duty under international law to not block water access to
Gaza. In November 2024 Barton stated he would resign in January 2025. Sir Philip became permanent secretary in 2020 but left before the full five-year terms achieved by his two predecessors. He was replaced by
Sir Oliver Robbins. Prior to leaving, Barton had objected to the appointment of
Peter Mandelson to be UK ambassador to the USA, the issue which also led to the dismissal of Robbins in April 2026. ==Honours==