[2] Riley was called to the bar at the Inner Temple on 23 November 1847, but early in life he began hack work for booksellers to make a living, by editing and translation.
On the creation of the Historical Manuscripts Commission (by royal charter in April 1869), Riley was engaged as an additional inspector for England, and given the task of examining the archives of various municipal corporations, the muniments of the colleges at Oxford and Cambridge, and the documents in the registries of various bishops and chapters.
For Bohn's Classical Library, Riley translated: His Dictionary of Latin Quotations (1856 and 1860), was included in the same series, and reprinted in 1866.
For Bohn's Antiquarian Library, he translated the Annals of Roger de Hoveden (1853, 2 vols.
For the Rolls Series, he edited the Munimenta Gildhallae Londoniensis, including the Liber Albus (1859), the Liber Custumarum (1860, in two parts), with a translation of the Anglo-Norman passages, and a glossary (1862); the Chronica Monasterii S. Albani, comprising the Annals of John Amundesham (1870 and 1871, 2 vols.