He inherited a collection of manuscripts in 1859, known as the Hengwrt collection, from his kinsman Sir Robert Vaughan, 2nd Baronet. The collection had been assembled by the 17th-century antiquarian Robert Vaughan and it contained an early version of the Canterbury Tales, mystery plays in Cornish and many early Welsh manuscripts, including twelve manuscripts of the Welsh laws of Hywel Dda. Wynne catalogued the manuscripts, publishing the result in Archaeologia Cambrensis between 1869 and 1871, and allowed scholars to examine and copy them.[2]
Wynne had considerable knowledge about the history and genealogy of north Wales, assisting other writers and contributing articles on Merionethshire to Archaeologia Cambrensis and elsewhere. He also wrote a history of Harlech Castle in 1878. He died on 9 June 1880.[2]