During the First World War he was head of the British military mission with the Russian Stavka with direct access to Tsar Nicholas II.

In December 1909 he was promoted to temporary brigadier general in charge of administration (Scotland),[1] holding this post until 1914.

David Lloyd George later recorded in his War Memoirs (published in the 1930s) that he was charming, hardworking and able to point out faults without causing offence.

He was in charge of the British Prisoners of War Department at The Hague from August 1917 to March 1918 and at Bern from April 1918 to December 1918.

Hanbury-Williams was Colonel Commandant of the Oxfordshire and Buckinghamshire Light Infantry from 1918 to the time of his death when he was succeeded in the post by General Sir Bernard Paget.

John Hanbury-Williams married Annie Emily, youngest daughter of Emil Reiss, in 1888, with whom he was to have four children.

[6] In later life Sir John Hanbury-Williams resided in an apartment in the Henry III Tower at Windsor Castle, where he died on 19 October 1946, on his eighty-seventh birthday.