Since when he Francis Wallace Grenfell's rank in the British Army been the highest rank?
Field marshal (United Kingdom) Field Marshal has been the highest rank in the British Army since 1736. A five-star rank with NATO code OF-10, it is equivalent to an Admiral of the Fleet in the Royal Navy or a Marshal of the Royal Air Force in the Royal Air Force (RAF). A Field Marshal's insignia consists of two crossed batons surrounded by yellow leaves below St Edward's Crown. Like Marshals of the RAF and Admirals of the Fleet, Field Marshals traditionally remain officers for life, though on half-pay when not in an appointment. The rank has been used sporadically throughout its history and was vacant during parts of the 18th and 19th centuries (when all former holders of the rank were deceased). After the Second World War, it became standard practice to appoint the Chief of the Imperial General Staff (later renamed Chief of the General Staff) to the rank on his last day in the post. Army officers occupying the post of Chief of the Defence Staff, the professional head of all the British Armed Forces, were usually promoted to the rank upon their appointment.
Francis Philip Woodruff Frank Richards a.k.a. Francis Philip Woodruff DCM, MM (1883–1961) was a World War I soldier and author. Born in Monmouthshire, he was orphaned at the age of nine, and was then brought up by his aunt and uncle in the Blaina area of the South Wales Valleys in industrial Monmouthshire. The uncle, his mother's twin brother, and surnamed Richards, adopted Frank who then changed his surname. During the 1890s Frank Richards worked as coal miner and joined Royal Welch Fusiliers in 1901, serving in the British Empire forces in British India under the British Raj and Burma from 1902 to 1909, after which he transferred to the reserves. He is best known as the author of one of the most widely acclaimed memoirs of the Great War to be written by a ranker, "Old Soldiers Never Die".