This 1241 treaty ended Henry III's invasion of Wales, forcing Dafydd ap Llywelyn to cede territory and surrender a rival claimant, curtailing Welsh autonomy.
Key Facts
- Date signed
- 29 August 1241
- Territory ceded
- Large parts of modern-day Flintshire
- Hostage surrendered
- Gruffudd ap Llywelyn Fawr, imprisoned in Tower of London
- Follow-up treaty
- Treaty of London, October 1241
- End of constraint
- Gruffudd died in escape attempt on 1 March 1244
By the Numbers
Location
Cause → Event → Consequence
Henry III launched an invasion of Wales in August 1241, pressuring Dafydd ap Llywelyn, prince of Wales, who faced both English military force and the internal dynastic threat posed by his half-brother Gruffudd ap Llywelyn Fawr, a rival claimant to the Welsh princeship.
The Treaty of Gwerneigron, signed on 29 August 1241 and supplemented by the Treaty of London in October, required Dafydd to cede large parts of Flintshire to Henry III, hand over his half-brother Gruffudd as a hostage, and pledge loyalty to the English crown, with Henry named as Dafydd's heir should he die without offspring.
Henry used Gruffudd's imprisonment as leverage to restrain Dafydd's ambitions until Gruffudd died in an escape attempt from the Tower of London on 1 March 1244. Free of that threat, Dafydd immediately invaded Flintshire and recovered the ceded territories, resuming Welsh resistance to English overlordship.
Political Outcome
Dafydd ap Llywelyn ceded Flintshire territory to Henry III, surrendered his half-brother Gruffudd as a hostage, and acknowledged English suzerainty; Welsh expansionist ambitions were temporarily suppressed.
Dafydd ap Llywelyn held Flintshire territories and exercised relatively independent authority as Prince of Wales
Henry III gained Flintshire lands and leverage over Wales through custody of Gruffudd, becoming Dafydd's feudal overlord and designated heir