Iain Moncreiffe of that Ilk

Sir Rupert Iain Kay Moncreiffe of that Ilk CVO, QC
Bust of Sir Iain Moncreiffe in the Register House, Edinburgh
Born	April 9, 1919
Died	February 27, 1985 (1985-02-28) (aged 65)
Occupation	Officer of Arms, genealogist
Nationality	British
Alma mater	University of Edinburgh Christ Church, Oxford
Subject	Genealogy, heraldry
Notable works	Simple Heraldry (1953) Blood Royal (1956) The Highland Clans (1967)
Spouse	Diana Hay, 23rd Countess of Erroll 1946-1964 Hermione Patricia Faulkner 1966-1985 (his death)
Children	Merlin Hay, 24th Earl of Erroll Peregrine David Moncreiffe of that Ilk Alexandra Moncreiffe Hay

Sir Rupert Iain Kay Moncreiffe of that Ilk, 11th Baronet, CVO, QC (9 April 1919 – 27 February 1985) was a British Officer of Arms and genealogist.

Moncreiffe was the son of Lieutenant-Commander Gerald Moncreiffe, RN, and Hilda, daughter of the Comte de Miremont, he succeeded his cousin as 11th Baronet and Chief of Clan Moncreiffe in 1957.

Educated at Stowe School, Heidelberg, and Christ Church, Oxford, as a cadet officer Moncreiffe trained with Derek Bond (actor) and Patrick Leigh Fermor, he later served in the Scots Guards during the Second World War, then as attaché at the British embassy in Moscow, before studying Scots Law at the University of Edinburgh, where he graduated PhD with a thesis on the Scots law of succession to peerages.

A prominent member of the Lyon Court, Moncreiffe held the offices of Falkland Pursuivant (1952), Kintyre Pursuivant (1953), Unicorn Pursuivant (1955), and (from 1961) Albany Herald. He wrote a popular work about the Scottish clans, The Highland Clans (1967), and with Don Pottinger Simple Heraldry, Cheerfully Illustrated (1953), Simple Custom (1954), and Blood Royal (1956), but his interests also extended to Georgian and Byzantine noble genealogies. Lord of the Dance, A Moncreiffe Miscellany, edited by Hugh Montgomery-Massingberd encompassed his genealogical world-view.