The most senior civil servant at the Foreign Office, Sir Philip Barton, is to stand down in January, the BBC has learned.
Sir Philip became permanent secretary in the department in 2020 but will leave his post short of the full five-year terms achieved by his two predecessors.
He was strongly criticised by MPs in 2022 for his handling of the chaotic withdrawal of UK staff after the fall of Kabul to the Taliban.
Foreign Secretary David Lammy is understood to have praised Sir Philip for his integrity and reassuring presence.
But after the transition to the new government, the pair “agreed that it is time to begin the process to appoint a successor”.
The BBC understands Sir Philip announced his decision to in an email to all Foreign, Commonwealth and Development Office staff on Monday.
In his four years as head of the Diplomatic Service, Sir Philip has served under five foreign secretaries: Dominic Raab, Liz Truss, James Cleverly, Lord Cameron and Lammy.
He has previously held a number of public service roles, including as the Foreign Office’s director general, consular and security, and as the acting chair of the Joint Intelligence Committee in the Cabinet Office.
He was also the former high commissioner to Islamabad, deputy head of mission in Washington, and the director of foreign policy and coordinator for Afghanistan and Pakistan.
During the evacuation of Kabul in 2022, Sir Philip took a 17-day holiday – which he told the Parliamentary Foreign Affairs Committee he regretted.
Sir Philip claimed it was not clear Kabul would fall so quickly when he went on leave, but his absence was viewed as a failure of leadership, and he was criticised for weakening the FCDO’s response.
His departure means the government has yet another big civil service role to fill including the cabinet secretary, national security adviser and UK ambassador in Washington.