Lord Erroll is the son of Sir Iain Moncreiffe of that Ilk and Diana, Countess of Errol. He succeeded his mother, the countess, in 1978 as, and in 1985, his father as a Baronet. As Lord Erroll was Chief of Clan Hay by virtue of his mother"s title, his younger brother Peregrine took over their father as Chief of Clan Moncreiffe.
He was educated at Eton College and at Trinity College, Cambridge.
He was page to the Lord Lyon in 1956. He served in the 21st SAS Artists Rifles (V) Territorial Army from 1975 to 1990, and was an Honorary Colonel of the Royal Military Police (Territorial Army) from 1992 to 1997. He is also President of ERADAR the Chamber for Electronic Business, and Chairman of the Digital Policy Alliance (EURIM).
He is a director of Lasseo, a not-for-profit technical standardization and interoperability membership organisation for smartcard technologies.
Lord Erroll was one of 90 excepted hereditary peers elected to remain in the House of Lords following the House of Lords Acting 1999. A programmer and system designer by trade he sits as a crossbencher and usually speaks on matters relating to cybersecurity and information technology.
He is a member of the Council of the Hereditary Peerage Association. The has been a lieutenant at the Atholl Highlanders since 1974, and is a Member of the Royal Company of Archers. Erroll has worked as a marketing and computer consultant, is a Freeman of the City of London and a Member of the Court of Assistants of the Worshipful Company of Fishmongers, of which he was Prime Warden in 2000–2001.
He was a member of the Science and Technology Committee and criticised Tony Blair"s government for the failure to curb cyber crime after various government agencies, including the Ministry of Defence and Her Majesty Revenue and Customs, reported massive losses of data in 2008.
Most recently he was a member of the Information Committee from 2007 to 2012.
