A younger son of John Leslie senior, Bishop of Kilmore, Elphin and Ardagh and Isabella St. Lawrence [1] he was born at Dromore in November 1814.
He was educated in England at Harrow School,[2] before matriculating at Christ Church, Oxford in 1833.
[3] While studying at Oxford, he played first-class cricket on two occasions in 1836.
[4] A student of both King's Inns in Dublin and of Lincoln's Inn, he was called to the bar in 1840 and January 1841 respectively.
[1] Leslie died a day after his 83rd birthday in November 1897 at Albury, Surrey.