He was appointed to the chair of philosophy and later to that of theology at the University of Astorga, but he remained only a short time, for he decided to devote himself to journalism, and moved to Madrid.
Under the pseudonyms of Fray Gerundio and Pelegrin Tirabeque, he wrote many capilladas or essays on a great variety of subjects, including the political questions of the day.
According to Ferrer del Rio, he borrowed the pseudonym Fray Gerundio from the work of Father Isla.
The essays were collected as Capilladas (1837–40) and as Teatro social del siglo XIX (1846), the latter dealing with the manners and customs of the day.
Lafuente's chief work, by which he is best known, is his Historia general de España, which he published in Madrid (1850–1869, 30 volumes).