The Duke of York's Hand in Edmund Tudor's Death
It was in the wake of the Wars of the Roses, when King Henry VI's uterine brothers Jasper and Edmund Tudor were still on very good terms with Richard Plantagenet, Duke of York. Even this good, that both brothers, according to The Paston Letters, were likely to be arrested for treason when they jointed the Duke to London.

When the King, in January 1454, had been in an ill mental state. The Tudor brothers supported York at the council meeting when he received protectorship. Not even the 1st Battle of St. Albans seemed to have changed their support to York.
During York’s brief protectorate, attempts to discipline Griffith ap Nicholas in South-West Wales had failed but when Edmund did succeed in this four months after York had lost his protectorship for the second time, it may have been a great embarrassment to York. The significance of the whole campaign centered on York’s determination to assert his control over the government by acting as the legitimate constable of the Welsh castles and neutralizing potentially dangerous rivals in the area. At that point Edmund seems to become a rival to York. In April 1456 York’s men, Sir Walter Deveraux and his son-in-law Sir William Herbert, decided to make their move by gathering a force of about 2000 men from around Herefordshire and causing for many local skirmishes which escalated in June when an attempt was made for an invasion on Kenilworth, with affirmed intentions to kill the King.
From there William Herbert, Walter Deveraux and members of the Vaughan family joined their forces, proceeding their attentions on asserting York’s authority and headed for West Wales, for Carmarthen Castle, for Edmund. They immediately seized the castle and took Edmund prison. From there, they went on to other places in West-Wales, re-establishing York’s authority after he earlier had lost those in Westminster. It is not clear at all why William Herbert changed side in the first place, as from the early days he appears to be on good terms with both Edmund and his younger brother Jasper.
A phrase from a contemporary poem composed by the Welsh bard Lewys Glyn Cothi in 1452/1453 in praise of William Herbert supports this thought:
...If Jasper was being pounded,
he’d [=William] pound through a thousand
men.
The nobleman’s full of sincerity (that will serve him well);
Gwilym [=William] is true and skilled
for one God before everything else,
also for the Crown, kindly eagle,
and above for the earl of Pembroke and his men.
Unfortunately Edmund would not be able to demonstrate more of his abilities in Wales, for he died at Carmarthen Castle on 1 November 1456. Eventhough, suggested is the plague for a possible cause of death, an ample possibility, for Edmund’s sudden death so soon after the events of that summer, is that he had suffered from wounds caused by opposing the force led by agents of the Duke of York. It was clearly a great shock and gives inevitable suspicion of violence or neglect during his imprisonment,
Attempts to condemn the Deveraux-Herbert upheavals happened on 15 February 1457 at a Great Council, which opened at Coventry and closed some time before 14 March. Unfortunately there are no contemporary accounts of this council that survives but there is still the preface of 1459's act of attainder of the Duke and his followers. According to the preamble, the chancellor made divers rehearsals to the Duke of York which the Duke of Buckingham, on behalf of all the lords present, stated that the Duke of York could only lean on the King’s grace. Going on demanding York should be punished, should there be any repeat, but the preamble does not say of what. The document of the indictments makes no direct accusations to York which makes it difficult to directly blame him for Edmund’s death, even though Herbert and Deveraux had to appear before the oyer and terminer sitting at Hereford from 2 until 7 April 1457. For Herbert and Deveraux the legal process went on for a few months and at the end it is difficult to see why King Henry responded to these men like he did, Herbert received a general pardon but Deveraux was imprisoned.
Selected sources:
The Paston Letters, ed. J Gairdner, 6 vols (1904)
R.S.Thomas, ‘The Political career, estates and connection of Jasper Tudor, Earl of Pembroke and Duke of Bedford (d. 1495)’, PhD thesis, Swansea University (1971)
D. Bayani, 'Jasper Tudor, Godfather of the Tudor Dynasty' (fortcoming 2014)