Question: Since when he Francis Wallace Grenfell's rank in the British Army been the highest rank?
Sentence (from "Francis Grenfell, 1st Baron Grenfell"): Field Marshal Francis Wallace Grenfell, 1st Baron Grenfell, GCB, GCMG, PC (29 April 1841 – 27 January 1925) was a British Army officer.
Relevant evidence: Yes