Algernon Percy , 10th Earl of Northumberland Algernon Percy , 10th Earl of Northumberland , 4th Baron Percy , KG ( 29 September 1602 – 13 October 1668 ) was an English military leader and a prominent supporter of constitutional monarchy . Family background . Algernon Percy was the third , but eldest surviving , son of Henry Percy , 9th Earl of Northumberland , the so - called ' Wizard Earl . ' His mother was Dorothy Percy " née " Devereux , Countess of Northumberland , daughter of Walter Devereux , 1st Earl of Essex and sister of Robert Devereux , 2nd Earl of Essex , one of Elizabeth I ' s favourite s who was executed for treason in 1601 . In 1605 , the 9th Earl was accused of either participation or complicity in the Gunpowder Plot , and as a result , he was imprisoned in the Tower of London until 1621 . The 9th Earl exerted influence on young Algernon ' s education in spite of his imprisonment , and Algernon frequently stayed with the 9th Earl in the Tower for 4 or 5 days at a time . On the model of King James I ' s " Basilikon Doron " , the 9th Earl wrote an essay of advice to his son in 1609 . His sister , Lucy Hay " née " Percy , dowager countess of Carlisle , and his younger brother , Henry Percy , were members of the household of Charles I ' s queen , Henrietta Maria . Another sister , Dorothy , was married to Robert Sidney , 2nd Earl of Leicester . Education and early years , 1615 – 24 . In 1615 , Algernon was sent to study at St John ' s College , Cambridge , and in 1616 he was admitted to the Middle Temple in London . He received his MA in 1616 and was made a Knight of the Bath , meaning he was now Sir Algernon Percy . In 1618 , Algernon and his tutor , Edward Douse , began a six - year tour of continental Europe , visiting the Netherlands , Italy , and France . Algernon returned to England in 1624 and joined his father , recently released from the Tower , at court . Public life before the Civil Wars , 1624 – 42 . Parliament . Algernon ' s first public service involved serving as MP for UK Parliament constituency during the " Happy Parliament " of 1624 – 25 and as MP for UK Parliament constituency during the " Useless Parliament " of 1625 – 26 . In March 1626 , Algernon was summoned to the House of Lords , assuming his father ' s barony and becoming known as " Lord Percy . " In November 1626 , he was appointed joint Lord Lieutenant of Cumberland , Westmorland , and Northumberland . Percy became a leader in the House of Lords of the faction opposed to Charles I ' s favourite , George Villiers , 1st Duke of Buckingham . First marriage . In 1629 , Algernon married Anne Cecil , daughter of William Cecil , 2nd Earl of Salisbury , " in spite of his father ' s deep disapproval , who said that ' the blood of a Percy would not mix with the blood of a Cecil if you poured it on a dish " ( Percy family history ) . ( The 9th Earl blamed the 1st Earl of Salisbury for his imprisonment in the Tower . ) The marriage , however , produced five daughters , including Anne ( d . 1654 ) , who married Philip Stanhope , 2nd Earl of Chesterfield , no issue , and Elizabeth ( 1636 – 1718 ) , who married Arthur Capell , 1st Earl of Essex . Upon the death of the 9th Earl in 1632 , Algernon Percy became the 10th Earl of Northumberland . Naval career . Throughout the early 1630s , the 10th Earl attempted to ingratiate himself with Charles I ' s court , initially unsuccessfully , although his family connections in the queen ' s household did manage to get him admitted to the Order of the Garter in 1635 . By 1636 – 37 , he was in good enough standing at court to be appointed admiral of the ship money fleet . Northumberland attempted to initiate naval reforms , often bypassing the lords of the admiralty and submitting his proposals directly to Charles I and the Privy Council . Although most historians would not consider Northumberland a Puritan , he did enforce the Oath of Supremacy on his fleet and removed three Catholic officers who refused to take the oath . Northumberland ' s first expedition as admiral in 1636 was to force Dutch ships fishing in waters claimed by England to purchase English fishing licenses , in exchange for which the English fleet would offer protection from the Dunkirkers . If Dutch sea captains refused to purchase the licenses , their nets were cut . Northumberland was less enthusiastic about his second expedition as admiral , which was to transport Spanish money to the Netherlands in 1637 . Northumberland ' s political faction was strongly pro - French and anti - Spanish , so he rankled at the thought of aiding the Spaniards . Lord High Admiral . In 1638 , two of Northumberland ' s prominent supporters at court — Thomas Wentworth and Archbishop of Canterbury William Laud — used their influence at court to have Northumberland made Lord High Admiral of England , a position which had been vacant since the assassination of the 1st Duke of Buckingham in 1628 . At the time he was appointed , it was understood that Charles I ' s son James would become Lord High Admiral upon attaining his majority , although the Civil Wars occurred before this could happen and Charles removed Northumberland from the post in 1642 . Events leading to the Civil Wars . In response to the rise of the Scottish Covenanters , who opposed the attempt to introduce the Book of Common Prayer in Scotland in 1637 , Charles I appointed an eight - man subcommittee of the Privy Council to deal with the issue . Northumberland ' s patron , Thomas Wentworth , favoured war with Scotland , while Northumberland did not want to go to war , and feared that his estates in northern England would be occupied during the hostilities . As such , when Wentworth had Northumberland appointed general of the English forces during the second of the Bishops ' Wars in January 1640 , Northumberland was happy to let illness prevent him from joining the army in the field , and Northumberland was entirely defeatist about the prospect of defeating the Covenanters militarily . In May 1640 , Northumberland was one of only two members of a subcommittee of the Privy Council who opposed the dissolution of the Short Parliament , a move that confirmed his break with Wentworth ( whom Charles had recently named Earl of Strafford ) and earned him the displeasure of the king . When the Long Parliament met , Northumberland became one of the leading critics of royal policy . During Strafford ' s trial for high treason and the subsequent bill of attainder against him , Northumberland gave evidence at his trial which , though favourable on the important point of bringing the Irish army to England , was on the whole damaging . Northumberland ' s brother Henry was involved in the First Army Plot of 1641 , an attempt to rescue Strafford from the Tower of London and to forcibly dissolve the Long Parliament . Northumberland encouraged his brother to write a letter exposing the royalist plot to rescue Strafford , and then , at John Pym ' s urging , agreed to allow Denzil Holles and John Hampden to publish this letter . The English Civil War , 1642 – 49 . Northumberland ' s role in the First English Civil War , 1642 – 46 . Break with the king . With the coming of the English Civil War , Northumberland became the highest - ranking member of Charles I ' s government to side with the Parliamentarians . His first action in open defiance of royal authority came in November 1641 , when he obeyed Parliament ' s instruction to prepare four ships to take men and arms under parliamentary control to Ireland to suppress the rebellion there . He did not , however , support the Grand Remonstrance . However , when James Stewart , 1st Duke of Richmond suggested in January 1642 that the parliament adjourn for six months , Northumberland led a protest which favoured sanctioning Richmond for breach of privilege . In February , Parliament named Northumberland Lord Lieutenant of Sussex , Pembrokeshire , and Anglesey . Northumberland subsequently voted in favour of the Militia Ordinance . During the subsequent fighting between royalist and parliamentary forces , Northumberland ' s control of the navy was a crucial factor in securing parliamentary victory As a result , Charles I removed Northumberland from the post of Lord High Admiral in late June 1642 and Northumberland relinquished the position . In July , he accepted a position on the parliamentary committee of public safety . Northumberland ' s support for the war wavered shortly thereafter , however , in the wake of setbacks faced by parliamentary forces in 1642 – 43 . Northumberland was also disappointed that Parliament chose Robert Rich , 2nd Earl of Warwick rather than himself as the new Lord High Admiral . Northumberland was apparently appalled by the violence of the Battle of Edgehill and the Battle of Turnham Green , and became the leader of a party favouring peace by early - to - mid - 1643 . Second marriage . Northumberland ' s first wife died of smallpox in 1637 . In October 1642 , he remarried , to Lady Elizabeth , daughter of Theophilus Howard , 2nd Earl of Suffolk and thus his first wife ' s cousin . Conversion to the peace faction . In April 1643 , Northumberland headed the parliamentary delegation to negotiate with Charles I at Oxford , but Charles was willing to grant little . Returning to London , Northumberland ' s peace party was increasingly attacked by the party favouring continued war : for example , in June , Northumberland was accused of complicity in Waller ' s Plot , though he was never prosecuted . In August , a leading hawk , Isaac Penington , the Lord Mayor of London instigated a plot whereby a number of lords were physically threatened , in the hopes that he would be able to have Northumberland arrested . After Northumberland was unable to convince his cousin , Robert Devereux , 3rd Earl of Essex to support further peace negotiations with the royalists , he retired to his estates at Petworth ( unlike other " peace lords " , who joined the king at Oxford at this time ) . Conversion to the war party . Northumberland did not remain at Petworth for long , though . Although he had opposed an alliance between parliament and Scotland against the king , following the passage of the Solemn League and Covenant in September 1643 , Northumberland returned to the capital and took the Covenant . He was soon appointed to the newly created Committee of Both Kingdoms , serving as its first chairman . Northumberland would gain a reputation as a supporter of the Scots on the committee — many speculated that this was because Scottish forces were occupying his lands in the north . Thus , although he continued to favour negotiations with Charles I , Northumberland was quickly coming around to the war party ' s position . Northumberland was one of only four lords to vote in favour of the Self - denying Ordinance . Soon , Northumberland would prove to be one of the greatest supporters of the New Model Army , with Northumberland ' s servant Robert Scawen chairing parliament ' s army committee . In March 1645 , Parliament made Northumberland guardian of Charles ' two young children , Princess Elizabeth and the Duke of Gloucester ( and also the Duke of York in July 1646 ) , and there was talk that Northumberland might be made king if negotiations with Charles failed . Following the failure of the negotiations at Uxbridge , Northumberland was thoroughly behind the war party , now known as the Independents . In spite of Northumberland ' s political conversion , he did not vote in favour of the bill of attainder against his old patron , Archbishop Laud . 1647 : Between the First and Second English Civil War . In early 1647 , Northumberland sided with Edward Montagu , 2nd Earl of Manchester and the Presbyterian party against the Independents as they attempted to draw up terms acceptable to the king . In the emerging dispute between parliament and the army , Northumberland sided with the army , and in July 1647 , Northumberland was one of nine peers who left Parliament for the army following riots around Westminster . Meetings were subsequently held between Northumberland and the army at Northumberland ' s property , Syon House . Northumberland led a final attempt to negotiate with Charles I in December 1647 , but this failed . Role in the Regicide . Following the Second English Civil War , most parliamentarians became increasingly disillusioned with Charles I and began to favour his execution . Northumberland attempted to halt this movement , opposing the Vote of No Addresses in January 1648 , and attempting to negotiate terms with the king at Newport until the end of 1648 . Northumberland would prove to be one of Charles I ' s greatest supporters in the Rump Parliament . When Parliament moved to try Charles I for treason in January 1649 , Northumberland was the leader of the forces in the House of Lords opposed to trying the king . Life during the English Interregnum , 1649 – 60 . Northumberland withdrew from public life following the execution of Charles I . In May 1649 , he was relieved of responsibility for the king ' s children and no longer had any official duties . Northumberland was briefly placed under house arrest in 1655 after John Thurloe accused him of encouraging his northern tenants to participate in the Penruddock uprising . Northumberland refused requests from both Oliver Cromwell and Richard Cromwell to sit in the upper house of their parliaments . Life following the Restoration , 1660 – 68 . With the coming of the Restoration in 1660 , Northumberland attempted to re - enter politics by organizing the Suffolk House cabal , which included Edward Montagu , 2nd Earl of Manchester , Denzil Holles , Oliver St John , and William Pierrepont , and which hoped to force on Charles II the terms offered to Charles I at Newport . This cabal collapsed when General Monck chose to support the Convention Parliament in April 1660 . With Charles II ' s return to England in May 1660 , Northumberland rushed to curry favour with the new king . He did however oppose the bill to execute the regicides responsible for Charles I ' s death . Charles II appointed Northumberland to his Privy Council in late May 1660 , and Northumberland was named Lord Lieutenant of Sussex in August and Lord Lieutenant of Northumberland in September . His return to politics was completed with his service as Lord High Constable of England at Charles II ' s coronation in April 1661 . Northumberland gained a reputation as a diligent enforcer of the Clarendon Code and as an efficient organizer of the militias . During the period of Restoration politics , Northumberland ' s closest ally at court was Edward Montagu , 2nd Earl of Manchester , while Edward Hyde , 1st Earl of Clarendon remained a constant enemy , a rivalry which climaxed with Northumberland voting in favour of Clarendon ' s impeachment in 1667 . Northumberland died at Petworth on 13 October 1668 and was buried there in September 1668 . His son Joceline succeeded him as 11th Earl of Northumberland .