English historian, whose career was dedicated to the study of the English Civil Wars.

He was educated at Winchester and Christ Church, Oxford, and for some years was a member of the Irvingite Church. From 1871 to 1885 he taught at King's College, London, becoming professor of modern history there in 1876. He was elected fellow of All Souls College, Oxford, in 1884 and of Merton College in 1892 but declined the regius professorship in 1894.

His researches among manuscript collections at Simancas, Venice, Rome, Brussels, and Paris, as well as in England, gave unrivalled authority to the monumental undertaking that took shape between 1863 and 1900. Its principal stages were the History of England From the Accession of James I to the Outbreak of the Civil War, 1603–1642, 10 vol. (1883–84); History of the Great Civil War, 1642–1649, 3 vol. (1886), 4 vol. (1893); and History of the Commonwealth and Protectorate, 1649–1660, 4 vol. (1903). In analyzing the cause of the Civil War, he showed keen perception of individual motives as well as broad understanding of the material factors underlying political conduct. He was ready to credit England with a sense of nationhood wider and deeper than any provided for by the mere forms of government, and this gave drama to his otherwise unadorned chronicle. Inconsistencies and misinterpretations may be found, but the authority of his History of England continues to command respect little short of that usually reserved for original sources.

Among the most noteworthy of his separate works are Prince Charles and the Spanish Marriage, 2 vol. (1869); Outline of English History (1st ed., 1881; later ed., 1919); Student's History of England, 2 vol. (1st ed., 1890–91; later ed., 3 vol., 1920); What Gunpowder Plot Was (1897); and Oliver Cromwell (1901). His edition of Constitutional Documents of the Puritan Revolution 1628–1660 (1889) continues to be widely used. He also edited collections of papers for the Camden Society and from 1891 was editor of the English Historical Review.