The first of them chronologically is the death of Edward of Lancaster, only child of Henry VI and Margaret of Anjou, at Tewkesbury. There are many contemporary sources, two of them written very soon after the battle of Tewkesbury. The first, a letter written by the Duke of Clarence on 6 May, says that Edward was killed in the battle. The Arrivall of Edward IV, Yorkist in sympathy and written only a month or so afterwards says that Edward was killed in the flight after the battle. There are five other accounts written in 1471 or soon after which confirm these statements, reiterated by the Lancastrian Warkworth in about 1478. No serious historian now doubts that Edward was killed in the fighting.
The continental sources are a different matter, and very soon after the battle, by 1473, atrocity stories appear, describing how the young prince was murdered in front of Edward IV. These stories were taken up by the later English chroniclers, those writing after the death of Richard III, and embroidered with enthusiasm. The first to mention Richrd of Gloucester as taking part in the murder was Vergil, writing in about 1516. It is interesting to note that no one accuses Gloucester only of the murder, he is always associated with Clarence and Hastings and later with Thomas Grey, Marquess Dorset. This whole matter is discussed in detail in Apendix 2 of P.W. Hammond, The Battles of Barnet and Tewkesbury, 1990.
The second murder occurring in 1471 is that of Henry VI. This may well have been a murder, it is difficult to take seriously the claim in the Yorkist Arrivall that he died of pure displeasure and melancholy, and his death so soon after that of his son seems unlikely to have been a coincidence. It could have been so of course, as has been pointed out by W.J. White in his discussion in ‘The Death and Burial of Henry VI, A Review of the Facts and Theories, Part I’, in The Ricardian, vol. 6,  pp.70-80. White shows also that the earliest sources noting the death of Henry do not name anyone as being personally responsible although the early continental writers assume that there was a murder and that Edward IV must have given the order for it. The first to name Gloucester as the murderer is probably the Frenchman Philippe de Commines writing about 1490 and the first English writer John Rous in his Historia de Regibus Anglie,written about the same time.
Following Rous the English writers embellish the story in much the same way as that of the death of Henry’s son although without adding so much detail. Discussions of Gloucester’s responsibility tend to centre on the date on which the death took place, since he was only in London from 21 May until the next day. Sir Clements Markham tried to show that Henry did not die until 24 May at least but this is certainly not so, and it seems most likely that Henry did die on the night of 21-22 May. Gloucester was undoubtedly in the Tower on that night, but then so was his brother Edward and a large number of other people. These dates are discussed by White and in Appendix 3 of Hammond Barnet and Tewkesbury. PWH