In July 2022 McDonald wrote a letter to the Parliamentary Commissioner for Standards stating that denials of previous allegations against Chris Pincher by the Prime Minister Boris Johnson were untrue.

[3][5] McDonald joined the Foreign and Commonwealth Office (FCO) in 1982 and served in Jeddah, Riyadh, Bonn and Washington, D.C. as well as in London.

[6][7] In September 2015, McDonald became Permanent Under-Secretary in the Foreign and Commonwealth Office and Head of the Diplomatic Service, replacing Sir Simon Fraser.

[12] He also revealed his office to be in "mourning" after the vote but stressed the importance of abiding by civil service impartiality in implementing the referendum result.

[13] In April 2020, McDonald stated to the Foreign Affairs Select Committee that it was a political decision to opt out of an EU scheme to bulk-buy ventilators and protective equipment for NHS workers to respond to the coronavirus pandemic.

[14] Following comments, Matt Hancock used Downing Street's daily press briefing to state that as far as he knew, there had been no political decision not to participate.

[21] A Guardian editorial described the letter as an "extraordinary, devastating intervention", which convinced Chancellor Rishi Sunak, Health Secretary Sajid Javid, and many others to resign from Boris Johnson's government from 5 July 2022.