The Foreign, Commonwealth & Development Office announced on 6 August 2026 that Thomas Allan had been appointed His Majesty's Ambassador to the Kingdom of Bahrain, succeeding Alastair Long, who was to move to another Diplomatic Service appointment. According to the announcement, Allan was planned to take up the post during January 2027.

The published CV lists Allan as FCDO Deputy Director for the Middle East and North Africa from 2023 to 2026. Earlier roles included Deputy Director at the Cabinet Office's National Security Secretariat from 2020 to 2022, Private Secretary to the Permanent Secretary at DFID from 2018 to 2019, and Deputy Head of Office at DFID Tanzania in Dar es Salaam from 2014 to 2017. He also served as an economic adviser in Yemen and Sierra Leone and as a policy officer at UNESCO in Addis Ababa.