[1] Following calls from Welsh graduates in law and students in the University of Oxford he and his two sons, Ieuan and Griffith, changed sides and supported Glyndŵr.
By a charter dated at Mathrafal, 6 July 1419, Sir Edward de Cherleton pardoned the murders and felonies committed by them on the occasion.
[1] At Shrewsbury, 4 March 1420, in the presence of Henry V and of Humphrey, Duke of Gloucester, the four acknowledged satisfaction by the Lord of Powys for their portion of the reward for the capture of Oldcastle.
[1] On 10 March 1420, the lordship of Broniarth was constituted a mesne manor in favour of Ieuan and Sir Griffith Vaughan, empowering the brothers to hold tri-weekly courts.
There is a persistent tradition that Gruffudd Vychan was in the band of Welshmen who are said to have saved the life of King Henry V when he rushed to rescue his brother, Humphrey, Duke of Gloucester, at the Battle of Agincourt, 1415.
A Welsh poet, in a cywydd, wrote that Gruffudd Vaughan was made an esquire in London and knighted in a town beyond Rouen in France.
A year later on 18 July 1444, his estates and those of his eldest son, Reynold, and nephew David Lloyd, were made over to John Sutton, 1st Baron Dudley.
[1] Vychan was summarily executed by Henry Grey, 2nd Earl of Tankerville at Powis Castle in 1447, in violation of a safe conduct given.
In the second of these Dafydd Llwyd o Fathafarn expresses the deep sense of anger and loss in Powys at the taking of his life:For the man with the golden collar whom I loved best, the breast is pining.
If thou art, tall hero, unrecorded killed, may God avenge thy beauteous brow.
Long may he hang Gruffudd was succeeded by his children David Lloyd (who inherited Garth), Cadwaladr, Reinallt (Reginald) Vychan, Gwenhwyvar, Catherine, Anne and Margaret.