Born Charles Leonard Augustus Parsons in Filey, East Riding of Yorkshire, England, he was the illegitimate[2] son of two middle class travelling entertainers.

Their hectic lifestyles prompted them to give up baby Leo, who was fostered out to (and later adopted by) a working-class couple, a Glasgow shipyard worker named James Blair and his wife Mary, taking their surname.

Blair next worked briefly in the Glasgow City Public Assistance Department before enlisting in the Royal Corps of Signals for service in the Second World War in 1942; he was demobilised with the acting rank of major in 1947.

Blair married Hazel Elizabeth Rosaleen Corscadden from a Protestant family in County Donegal, Ireland.

[4] Their first son, William Blair, a banking and finance law specialist, became a High Court judge.

In 1959, he was awarded a PhD from the University of Edinburgh for a thesis entitled "The legal status of the governmental employee".

He had ambitions to stand for Parliament in Durham, hoping to become a candidate in the 1964 general election, which were thwarted when he suffered a stroke in 1963 at the age of 40.