Born a U.S. citizen, the son of (Charles) Silas Baker (1888–1943), a Washington, D.C. attorney, and his wife Elizabeth Lambert, he attended Trinity College in Hartford, Connecticut and Harvard University, in the same class as Ted Kennedy. He married (and divorced) a French countess, Irene Le Gras du Luart de Montsaulnin, and they had two daughters; Nadia Elizabeth, b. 1965, who married Gregory, Jonkheer van Loudon, and Natasha Yolande D., b. 1968. In 1997 he remarried to Catherine Neville-Rolfe. Brooks-Baker preferred to be known as "Brookie" (to the extent that the record of his death in 2005 was made under both his real name and 'Brookie Brooks-Baker'). He adopted the "Brooks-" part of his surname voluntarily, perhaps because of a dispute with French authorities about his children's middle names.
He became a bond trader and settled in London in the 1960s. In 1974 Brooks-Baker and his business partners took over Debrett's, publisher of several titles on British aristocracy including Debrett’s Peerage & Baronetage.
In 1984 he moved to Burke's Peerage Partnership as director of publishing. The partnership had been in poor financial health for years and had already sold its flagship publication, Burke's Peerage, Baronetage & Knightage. Brooks-Baker was never associated with Burke's Peerage, Baronetage & Knightage but oversaw the publication of books about genealogy and the aristocracy including Burke's Presidential Families of the United States of America. The company's major business was genealogical research.
As public relations for Burke's, he was a frequent commentator on the British Royal family and aristocracy in the British press. He was famous for his ostentatious and oft-disputed pronouncements regarding British royalty, and for his advocacy of the most royal candidate theory of U.S. presidential succession. In 1986, he also controversially endorsed in a letter written to the British Prime Minister, Margaret Thatcher, a British royal ancestral connection with the Muslim prophet Muhammad. The Daily Telegraph would say in his obituary, "[H]is great advantage for journalists was that he was always available to make an arresting comment; his disadvantage was that he was often wrong."
He was once investigated by the FBI for an alleged scam in which he took money from people by claiming he would help them verify whether they were related to a billionaire who had died without known heirs.
He was often credited as 'H. B. Brooks-Baker'.
- Oxford Dictionary of National Biography, 2013, pg 44[full citation needed]
- "Harold Brooks-Baker, 71, U.S. Royal Watcher, Dies". The New York Times. Retrieved 2017-12-12.
- "Harold Brooks-Baker". The Daily Telegraph. 8 March 2005.
- "Is the Queen really a descendant of Prophet Mohammed?". The Week. 12 April 2018.
- "Harold Brooks-Baker, 71, U.S. Royal Watcher (obituary)". The New York Times. March 8, 2005.
- "Obituary of Harold Brooks-Baker Publisher whose frequent comments on the Royal Family were roundly dismissed by Buckingham Palace". The Daily Telegraph (London). March 8, 2005.