The sitter was the son of Rev. Archibald Moncrieff, minister of Blackford, Perthshire and his wife Catherine, daughter of John Halliday of Tulliebole, Kinrosshire, whom he married in 1739. William Moncrieff assumed the title circa 1750 after the baronetcy became dormant on the death of Sir Hugh Moncrieff in 1744. Sir William married Catherine (see lot 20) the eldest daughter of Robert Wellwood of Garvock on 13 April 1749. Catherine Wellwood was the niece of Henry Wellwood who bought the Tulliebole estate from the creditors of John Halliday's grandson, Robert and made it over to his niece's son Henry, the future 8th Baronet with the stipulation that he took the name Wellwood.
Educated at the University of Glasgow, William Moncrieff succeeded his father in the parish of Blackford, where he was minister from 1738 until his death in 1767. His eldest son, Sir Henry Wellwood, 8th Baronet succeeded his father as minister of Blackford. William Moncrieff died on 9 December 1767.