Unless specified otherwise, letters are addressed to, and correspondence is of, William Montagu, Marquess of Tweeddale (1826-1911), or his wife Candida Louise, Marchioness of Tweeddale. The 10th Marquess was known as Lord William Montagu Hay until he succeeded his brother, the 9th Marquess, in 1878. The 10th Marquess was succeeded in 1911 by his eldest son, William George Montagu, Marquess of Tweeddale (1884-1967), who was styled Earl of Gifford until that date.