Ralph de Diceto (d. c. 1202) was archdeacon of Middlesex, dean of St Paul's Cathedral (from c. 1180), and author of two chronicles, the Abbreviationes chronicorum and the Ymagines historiarum.
He is first mentioned in 1152, when he received the archdeaconry of Middlesex. He was probably born between 1120 and 1130; of his parentage and nationality we know nothing. The common statement that he derived his surname from Diss in Norfolk is a mere conjecture. Dicetum may equally well be a Latinized form of Dissai, Dicy, or , place names in Maine, Picardy, Burgundy, and Champagne.
In 1152 Diceto was already a master of arts and, presumably, he had studied at Paris. His reputation for learning and integrity stood high. He was regarded with respect and favor by Arnulf of Lisieux and Gilbert Foliot of Hereford (afterwards of London), two of the most eminent bishops of their time. Quite naturally, the archdeacon took in the Becket question the same side as his friends.
By 1164 he had acquired the livings of Aynho, Northamptonshire, and Finchingfield, Essex, and served them both by vicars.
Although his narrative is colourless and although he was one of those who showed some sympathy for Becket at the council of Northampton (1164), the correspondence of Diceto shows that he regarded the archbishop's conduct as ill considered and that he gave advice to those whom Becket regarded as his chief enemies.
Diceto was selected in 1166 as the envoy of the English bishops when they protested against the excommunications launched by Becket. But, apart from this episode, which he characteristically neglects to record, he remained in the background. The natural impartiality of his intellect was accentuated by a certain timidity, which is apparent in his writings no less than in his life.
About 1180 be became dean of St Paul's. In this office he distinguished himself by careful management of the estates, by restoring the discipline of the chapter, and by building at his own expense a deanery house. A scholar and a man of considerable erudition, he showed a strong preference for historical studies; and about the time when he was preferred to the deanery he began to collect materials for the history of his own times.