| Honorific-Prefix: | Colonel The Right Honourable |
| The Earl of Erroll | |
| Office: | Member of the House of Lords |
| Status: | Lord Temporal |
| Term Label1: | as a hereditary peer |
| Term Start1: | 30 June 1978 |
| Term End1: | 11 November 1999 |
| Predecessor1: | The 23rd Countess of Erroll |
| Successor1: | Seat abolished |
| Term Label: | as an elected hereditary peer |
| Term Start: | 11 November 1999 |
| 1Blankname: | Election |
| 1Namedata: | 1999 |
| Predecessor: | Seat established |
| Birth Name: | Merlin Sereld Victor Gilbert Hay |
| Birth Date: | 1948 4, df=yes |
| Residence: | Woodbury Hall, Sandy, Bedfordshire |
| Office3: | Lord High Constable of Scotland Chief of Clan Hay |
| Termstart3: | 16 May 1978 |
| Predecessor3: | The 23rd Countess of Erroll |
| Children: | 4 |
| Father: | Sir Iain Moncreiffe, 11th Bt |
| Mother: | Diana Hay, 23rd Countess of Erroll |
| Occupation: | Programmer |
Merlin Sereld Victor Gilbert Hay, 24th Earl of Erroll (born 20 April 1948), is a crossbench member of the House of Lords, chief of the Scottish clan Hay, and hereditary Lord High Constable of Scotland.[1]
Lord Erroll, elder son of Diana Hay, 23rd Countess of Erroll and Sir Iain Moncreiffe of that Ilk, was a Page to the Lord Lyon in 1956. He was educated at Eton College before going up to Trinity College, Cambridge.[2]
Succeeding his mother, the Countess, in 1978 as Earl of Erroll, and in 1985, his father as a baronet, Lord Erroll now serves as a member of the Council of the Hereditary Peerage Association.[3] Whilst Lord Erroll inherited Chieftainship of Clan Hay via his mother, their father's Chieftainship of Clan Moncreiffe devolved to his younger brother Peregrine.
He married Isabelle Jacqueline Laline Astell Hohler (Brussels, 22 August 1955 – 13 January 2020), daughter of Major Thomas Sidney Hohler and his wife, heiress to the Astell family, of Everton House, Bedfordshire,[4] in 1982. The Countess was a Patroness of the Royal Caledonian Ball[5] and served as High Sheriff of Bedfordshire in 2015.[6]
The Earl and Countess had two sons and two daughters:
The Earl of Erroll became a Lieutenant at the Atholl Highlanders since 1974,[2] and is a Member of the Royal Company of Archers.[10] 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.[11]
Lord Erroll has worked as a marketing and computer consultant,[2] is a Freeman of the City of London,[2] and Prime Warden of the Worshipful Company of Fishmongers (2000–01).[12] He continues to head the Puffin's Club, founded by his father.[13] He is President of ERADAR, an e-business consultancy,[14] and is President of the Digital Policy Alliance (EURIM).[15]
He was a director of LASSeO, a not-for-profit technical standardization and interoperability membership organisation for smartcard technologies.[16]
Lord Erroll was one of 90 excepted hereditary peers elected to remain in the House of Lords following the House of Lords Act 1999.[17] A programmer and system designer by trade,[18] he sits as a crossbencher and usually speaks on matters relating to cybersecurity and information technology. He was a member of the Science and Technology Committee and criticised Gordon Brown's government for what he said was a failure to curb cybercrime after four government agencies, including the Ministry of Defence and HM Revenue and Customs, reported massive losses of data in 2008.[18] Most recently he was a member of the Information Committee from 2007 to 2012.[17]
Lord Erroll served as Lord High Constable of Scotland at the coronation of King Charles III and Queen Camilla in 2023.[19] [20]