Joan was the illegitimate daughter of King John of England. Her early life is undocumented, but around 1205 (the exact date is unclear) she abruptly entered history when she was married to Llywelyn the Great. This was a diplomatic marriage intended to strengthen the potentially strained relationship between the English Crown and the prince of Gwynedd – and indeed Joan did successfully mediate between her husband and her father on several occasions.
However, by 1211 the two men were at war. King John had invaded north Wales and was in a position to crush Llywelyn once and for all. Joan was sent to soften her father’s anger, and although the prince had to surrender much land to John and pay a hefty tribute, he was not entirely dispossessed. After Henry III came to the throne in 1216, Joan continued to plead Gwynedd’s cause to the English court.
It is for the drama of her domestic life that the ‘Lady of Wales’ is probably best remembered. In 1230 Joan was caught committing adultery with William de Braose, an English nobleman with whom Llewelyn was negotiating a political alliance. The prince dealt with the situation swiftly and brutally: Joan’s lover was summarily executed and she was placed under house arrest. The following year she seems to have been forgiven, however, and the two lived in apparent happiness until her death at Abergwyngregyn in 1237. These events are dealt with powerfully in a well-known Welsh language drama by Saunders Lewis called Siwan (– Welsh for Joan).
Joan was buried at Llanfaes on the coast of Anglesey facing Abergwyngregyn – in order, so it is said, that Llewelyn could gaze across the Menai Strait and see his beloved’s final resting place. He founded a Franciscan Friary at the site, which prospered until the English conquest of Gwynedd in 1283 and Joan’s coffin can still be seen in the porch of Beaumaris parish church.