[3] During the First World War, Thomson first served at the British Expeditionary Force Headquarters and was Chief Military Interpreter between Sir John French and General Joffre.

But when there he quickly formed the view that an unprepared and ill-armed Romania facing a war on three fronts against Austria-Hungary, Turkey and Bulgaria would be a liability rather than an asset to the allies.

[8] In 1924, however, newly elected Labour Prime Minister Ramsay MacDonald elevated him to the peerage as Baron Thomson, of Cardington in the County of Bedford.

[10] He served as Secretary of State for Air in MacDonald's first short lived Labour administration of 1924[11] – interrupting briefly Sir Samuel Hoare's seven-year grip on the post.

In March 1915, while British military attache in Bucharest, he met the (married) French-Romanian author Princess Marthe Bibesco, and remained devoted to her for the rest of his life.

[14] His second term in office was cut short by tragedy as Thomson died in the crash of the R101 airship, a government-designed dirigible, on its maiden flight to Karachi in October 1930.