John and Isabelle accompanied Warwick in escorting the French King's envoys to Canterbury. However, by this time, it was being rumoured that Warwick was moving towards supporting the House of Lancaster, as a result of dissatisfaction over the king's marriage to Elizabeth Woodville and his pursuit of an anti-French foreign policy. In 1469, Warwick organised Robin of Redesdale's rebellion against Edward IV in Yorkshire and in July that year the king's brother George, Duke of Clarence married Warwick's daughter Isabelle whilst anchored off Calais; this was in direct defiance of the king's own wishes. It seems that Montagu, however, reacted strongly against his brother's machinations, and, unlike him, was satisfied with his current position. On 27 October 1469, Henry Percy had taken his oath of fealty to the King, and had been released from the Tower. The following year saw the return of Robin of Redesdale and another rebellion on behalf of Warwick. Montagu was forced to come down from the Scottish border to suppress it; this he did, but, one historian has suggested, albeit that he "allowed the leaders to escape ... ensuring that the rebellion could rise again" at a more opportune moment. Almost immediately, Montagu was forced to crush another rebellion, this time led by a Robin of Holderness, but calling for the return of Percy to the Northumberland Earldom. The Redesdale rebels soon reformed into an army big enough to march south and defeat a royal force at the Battle of Edgecote Moor on 26 July 1469. King Edward still accepted that Montagu was uninvolved in his brother's rebellion, and in the event, Montagu was the only Neville to accompany the king on his journey from the north back to London. However, it was while Edward was in York that he ordered the rehabilitation of Henry Percy to his family Earldom on 25/27 March 1470. On the same day John was elevated to the Marquessate of Montagu, and now outranked his brother, an Earl, in the English peerage. Historians have since questioned, however, whether his new title had the gravitas that his previous Earldom had had, and have even suggested that the king was "walking a tightrope" as to whether Montagu would actually accept it or not. To compensate him for the loss of the Percy estates Montagu was granted the lands of the dead Earl of Devon, and Montagu's son, George was created Duke of