Source: A Baronial Family in Medievil England: The Clares, 1217-1314, Michael Altschul, The Johns Hopkins Press, Baltimore, 1965.
From same, p 92: "On July 15, 1262, the day after the king sailed to
France, Earl Richard de Clare died. Two weeks later he was buried at
Tewkesbury Abbey. The earl had not played a conspicuous role in the baronial
movement since the settlement of 1261; he had been in ill health for some
months before his death, and rumors circulated that he had been poisoned.
[Footnote by Altschul: "E.g., Dunstable, p. 219' *Annales Cambriae*, pp. 99-100, where "Gilbert" is wrongly given for "Richard." These chronicles have probably confused the earl's natural death with the alleged poison plot of 1258."]" [Was Richard maybe poisoned at the instigation of Simon de Montfort or some of his allies?] Henry had settled with the rebellious barons in 1261 (p 92). Richard de Clare had at first sided with the barons in the antiroyalist
movement which began in the summer of 1258 or thereabouts (p 82-87), but
appears to have withdrawn support shortly after December 1258 (p 87).
Richard de Clare, 6th Earl of Hertford and 2nd Earl of Gloucester, then in minority at the decease of his father in 1229. The wardship of this young nobleman was granted to the famous Hubert de Burgh, Earl of Kent, Justiciary of England, whose dau., Margaret, to the great displeasure of the king (Henry III), he afterwards (1243) clandestinely married but from whom he was probably divorced, for we find the king marrying him the next year to Maude, dau. of John de Lacy, Earl of Lincoln, in consideration whereof the said John paid to the crown 5,000 marks and remitted a debt of 2,000 more. His lordship, who appears to have been a very distinguished personage in the reign of Henry III, was one of the chief nobles present in Westminster Hall (40th Henry III) [1256], when Boniface, archbishop of Canterbury, with divers other prelates, pronounced that solemn curse, with candles lighted, against all those who should thenceforth violate Magna Carta. In two years afterwards, an attempt was made by Walter de Scotenay, his chief counsellor, to poison the earl and his brother William, which proved effective as to the latter, while his lordship narrowly escaped with the loss of his hair and nails. In the next year the earl was commissioned, with others of the nobility by the appointment of the king and the whole baronage of England, to the parliament of France to convey King Henry III's resignation of Normandy and to adjust all differences between the two crowns; and upon the return of the mission, his lordship reported proceedings to the king, in parliament. About this period he had license to fortify the isle of Portland and to embattle it as a fortress. It is reported of this nobleman that, being at Tewkesbury in the 45th Henry III [1261], a Jew, who had fallen into a jakes upon the Saturday, refusing to be pulled out in reverence of the Jewish sabbath, his lordship prohibited any help to be afforded him on the next day, the Christian sabbath, and thus suffered the unfortunate Israelite to perish. He d. himself in the July of the next year (1262), having been poisoned at the table of Peter de Savoy, the queen's uncle, along with Baldwin, Earl of Devon, and other persons of note. His lordship left issue, Gilbert, his successor, Thomas, Rose, and Margaret. The earl was s. by his elder son, Gilbert de Clare. [Sir Bernard Burke, Dormant and Extinct Peerages, Burke's Peerage, London, 1883, p. 119, Clare, Lords of Clare, Earls of Hertford, Earls of Gloucester]
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Richard de Clare, 7th Earl of Gloucester, 8TH EARL OF CLARE, 6TH EARL OF HERTFORD (b. Aug. 4, 1222--d. July 15, 1262, Eschemerfield, near Canterbury, Kent, Eng.), the most powerful English noble of his time. He held estates in more than 20 English counties, including the lordship of Tewkesbury, wealthy manors in Gloucester, and the great marcher lordship of Glamorgan. He himself acquired the Kilkenny estates in Ireland and the lordship of Usk and Caerleon in south Wales, making him the greatest lord in south Wales; in Glamorgan especially he was almost an independent prince.
Son of Gilbert de Clare (the 6th Earl), Richard succeeded to the earldoms in October 1230. He refused to help King Henry III on the French expedition of 1253 but was with him afterward at Paris. Thereafter he went on a diplomatic errand to Scotland and was sent to Germany to work among the princes for the election of his stepfather, Richard, Earl of Cornwall, as king of the Romans. About 1258 Gloucester became a leader of the barons in their resistance to the king, and he was prominent during the proceedings that followed the Mad Parliament at Oxford in 1258. In 1259, however, he quarreled with Simon de Montfort, Earl of Leicester; the dispute, begun in England, was renewed in France, and he was again in the confidence of the king. This attitude, too, was only temporary, and in 1261 Gloucester and Montfort were again working in concord. [Encyclopaedia Britannica CD, 1996, GLOUCESTER, RICHARD DE CLARE, 7TH EARL OF]