In 1777 Thomas Frewen received the bequest of Cold Overton Hall in Leicestershire from the Turner family, on the condition that he should adopt the surname and arms of the Turners, which he accordingly did, uniting it to Frewen in a double barrel.
John was educated at Rugby School and Queen's College, Oxford, where he graduated BA in 1778.
He inherited Cold Overton Hall at his father's death in 1791, and adopted the name and arms of Turner at that time for the same purpose.
He became Lieutenant-Colonel of Leicestershire Yeomanry in 1797, and MP for the Irish seat of Athlone, Westmeath from 1807 to 1812.
His funerary monument in the church at Cold Overton is by William Grinsell Nicholl.