The papers' greatest importance is for colonial history, although they also contain much material of interest for domestic politics, and for Grey's period at the War Office. During his years as Colonial Secretary in the government of Lord John Russell, 1846-1852, the papers include private letters from some fifty colonial governors, often explaining and amplifying their dispatches. Nor did the 3rd earl's interest in colonies cease when he left office. He was still writing pamphlets on colonial topics when nearly ninety, and colonial governors continued to consult him in his latter years.
Although Grey never again held ministerial office after 1852, he continued to be active in the House of Lords, and he maintained a vigilant interest in public policy until the end of his life. In his early career he had proved an active supporter of Catholic emancipation and parliamentary reform. In later life Ireland continued to be among his foremost interests, and he became a determined opponent of Gladstone's Home Rule policies. Free trade, parliamentary reform, church affairs, foreign policy, land, tithes, bimettalism, and the housing of the poor all engaged his attention and his pen. His correspondents included many prominent churchmen, and a number of well-known women, among them Florence Nightingale and Josephine Butler. One of his most frequent correspondents was his brother-in-law, Charles Wood, 1st Viscount Halifax. Among his most enduring interests was his estate at Howick in Northumberland, and, although the main series of Grey Estate Papers forms a separate division of the Earl Grey Papers, there is much material in the 3rd Earl's papers relating to estate matters and to Northumberland affairs.