Patrick Montague-Smith was born in 1920, the only child of Major Vernon Montague-Smith and his wife Sybil, daughter of William Bourne. He was educated at Mercers' School, and served in the RASC from 1940 to 1946, after which he joined Debrett as Assistant Editor, becoming Editor on his predecessor’s retirement in 1962.
Among his books are Royal Line of Succession in 1853 and The Royal Wedding of H.R.H. Princess Anne and Captain Mark Phillips in 1973 and also Debrett’s Correct Form, which has been published in three editions, 1970, 1976, and 1978. He is also well known for one other book, Country Life Book of the Silver Jubilee, which was a best seller in 1977. He also wrote numerous other books and articles for national magazines and newspapers and established himself as the ultimate authority on the Peerage and Baronetage. He was a fellow of the Society of Genealogists and was widely regarded as one of the foremost genealogists in Great Britain. He died in 1986.