Earl of Londonderry extinct on the death of his great-grandson, the fourth Earl, in 1714. The second creation came in 1726 in favour of the soldier and politician Thomas Pitt, 1st Baron Londonderry. He had already been created Baron Londonderry in 1719 and was made Viscount Gallen-Ridgeway at the same time as he was granted the earldom, also in the Peerage of Ireland. He was the husband of Lady Frances Ridgeway, daughter and heiress of the fourth Earl of the first creation. A member of the prominent Pitt family, he was the uncle of William Pitt, 1st Earl of Chatham. His younger son,
George Mackenzie, 3rd Earl of Cromartie 1748. He died on 28 September 1766 in Soho Square, London, having never gone north of the River Trent again, in keeping with the terms of his pardon. He married Isabel Gordon, daughter of Sir William Gordon of Invergordon, on 23 September 1724 and had a large family of young children in 1746. His numerous children, three sons, and nine daughters, were: George Mackenzie, 3rd Earl of Cromartie George Mackenzie, 3rd Earl of Cromartie (c. 1703–28 September 1766) was a Scottish nobleman. He succeeded his father John, the 2nd earl, in February 1731. In 1745, he joined Charles Edward Stuart