 His maternal grandfather was Colonel George Lionel Dawson-Damer and his paternal uncle was Charles Powell Leslie, also a Member of Parliament.His ancestor, the Right Reverend John Leslie, Bishop of the Isles, moved from Scotland to Ireland in 1633 when he was made Bishop of Raphoe in County Donegal and was subsequently made Bishop of Clogher in 1661.Leslie was commissioned into the Grenadier Guards, with whom he served as a lieutenant at the Battle of Tel el Kebir in 1882, distinguishing himself under fire.