John Mordaunt, 1st Viscount Mordaunt of Avalon (1626-1675), royalist conspirator. In 1648 he joined his elder brother Henry Mordaunt, 2nd Earl of Peterborough, in a royalist uprising. John raised 200 horsemen for the king, but the rising failed and he, along with his brother, fled into exile, staying for a time at The Hague. Mordaunt had returned to England by 1652, when a challenge to a duel from Brian Cockayne ended in a brief stay in the Tower.
He was on the fringes of royalist conspiracy throughout the early and mid-1650s, but did not play an important role until after his marriage in May 1657 to the daughter of Thomas Carey, second son of Robert, earl of Monmouth. That year he promised 400 or 500 men for Charles II, and in 1658 he plotted with the Marquess of Ormond, in England on a secret visit. A royalist turncoat, John Stapley, betrayed Mordaunt and he was arrested on 1 April 1658 and later charged with treason. Mordaunt avoided the block by a mixture of judicious bribery and blind luck. Released shortly afterwards Mordaunt immediately returned to his work for the king. A mark of the king's favour came in March 1659, when he signed a warrant for Mordaunt's viscountcy as Viscount Mordaunt of Avalon. Despite this, however, bitter divisions among the royalists continued. About June 1659 Mordaunt returned from a trip to Brussels prepared to lead a new rising, but continuing bickering among royalists and the efficiency of the government's intelligence doomed Mordaunt's plans; when Mordaunt finally appeared for the king in early August only thirty men turned up, narrowly avoiding capture. Mordaunt hid in London until he could make his escape to France in September 1659. Indefatigable as ever he soon returned to London, where he worked to advance the king's fortunes, plotting a French invasion and yet another uprising. But during these months Mordaunt's credit was on the wane at court. The Viscount's effectiveness was further reduced as his relations with the Presbyterians frayed over their insistence upon a conditional restoration.
Despite these setbacks Mordaunt remained among the most active and well-known royalist conspirators. He was again in France in November 1659, consulting with the king and arguing fruitlessly for a French invasion. Mordaunt was among the thousands who welcomed Charles II to Dover on 25 May, and Charles knighted him there. Although Mordaunt devoted a dozen years to the king's cause - he was certainly among the most active, if not the most successful, of royalist conspirators - his rewards were comparatively modest. Charles named him lord lieutenant of Surrey and gave him command of a regiment of horse. The king also appointed him governor of Windsor Castle and ranger of the forest there, and gave him the keepership of the Great Park of Windsor.
Source: Victor Stater, 'Mordaunt, John, first Viscount Mordaunt of Avalon (1626-1675)', Oxford Dictionary of National Biography, Oxford University Press, 2004. By permission of Oxford University Press - http://dx.doi.org/10.1093/ref:odnb/19168.