David Hanmer was an English judge who lived in Wales, and is best-known as the father-in-law of Owain Glyndwr.

Although its roots were English, the Hanmer family was just as much Welsh. This was quite common for border families of such standing. David Hanmer had strong Welsh connections. His father Philip had married the daughter of a Welshman from Maelor Saesneg who rejoiced in the striking Welsh name of Dafydd ap Rhirid ab Ynyr ap Jonas of Llanerch Banna; she became Hanmer’s mother. Hanmer himself had married into another prominent Welsh family when he had taken as his bride Angharad, a daughter of Llywelyn Ddu ap Gruffudd ab Iorwerth Foel one of the most prominent Welshmen in nearby Chirkland . Angharad bore David at least four children: a daughter, Marged, and three sons, Gruffudd, Philip and John. Gruffudd was the eldest son: he became the acting legal attorney to the principality of North Wales. John held important posts in the government of Flintshire. Philip was also probably a lawyer. All four children were probably Welsh speaking, as may have been their father and certainly their mother. In 1377, Hanmer was appointed as one of the King’s Serjeants at Law and as such attended the parliament at Gloucester in 1378 and that at Northampton two years later at which he was also a member of the Commons for Herefordshire. In February 1383, he was made a Justice of the King’s Bench. This was a hugely important position and one of the highest to which a lawyer could aspire. It entailed his sitting in judgement on cases brought before the king. His greatest claim to fame, however, is that his daughter Marged married Owain Glyn Dwr, probably in 1383. Hanmer died about 1387.