Born in Chester in 1953, Lord Blair came up to Christ Church in 1971 to read English Language and Literature. Upon graduation in 1974, he signed up to the Metropolitan Police’s High Potential Development Scheme for Graduates, and over the course of a decade he served as a Constable, Sergeant and Inspector in both uniform and CID. In 1985, as a Detective Chief Inspector, Lord Blair took charge of CID at Kentish Town in North London where, as well as conducting a number of major enquiries, he was responsible for the identification of those killed at the King’s Cross disaster. Also in 1985, he published the book Investigating Rape: A New Approach for Police, which had a major impact on the way in which the police investigate serious sexual assault.

In 1988, as a Superintendent, Lord Blair managed the Metropolitan Police Crime Investigation Project, which redesigned the purpose and structure of local CID offices throughout London. In 1991, he was promoted to Chief Superintendent and appointed Staff Officer to Her Majesty's Chief Inspector of Constabulary, based at the Home Office. On his return to the Metropolitan Police in 1993, he was appointed the officer in charge of Operation Gallery – at the time the largest police corruption enquiry in London for a decade. He was appointed Assistant Chief Constable of Thames Valley Police the following year, becoming the deputy to the Chief Constable in 1997. The posting was short-lived, Lord Blair becoming Chief Constable of Surrey Police in January 1998. In 2000, he returned to the Metropolitan Police to serve as the Deputy Commissioner before becoming the Commissioner in 2005.

Lord Blair received a number of official honours over the course of his career, including the Queen's Police Medal for Distinguished Service, awarded in 1999, and a knighthood for services to policing awarded in the 2003 Queen’s Birthday Honours. He maintained his relationship with Christ Church throughout his life, receiving an Honorary Studentship (fellowship) in 2005 and chairing the Fabric Advisory Committee of Christ Church Cathedral from its inception in 2011 until 2023. He was appointed as a crossbench life peer in 2010, serving in the House of Lords until his death on Wednesday 9 July.