He afterwards, as Privy Councillor, attended the King to Scotland for his coronation, having by that time succeeded to his father’s titles and estates.
In 1636 he had the command of a noble fleet, the largest, says Lodge, since the death of Queen Elizabeth.
Lord Northumberland was much commended for his services in the expedition against the Dutch fishery, making advantageous terms for the King of England, after which he turned his time and thoughts to reforming many abuses then prevalent in the navy.
In 1637 he was named Lord High Admiral, and in 1639 commander of the troops marching against the Scots, but was prevented—so he pleaded—from joining the army by illness, when the real command devolved on the Earl of Strafford. Clarendon says, ‘Lord Northumberland was chosen for ornament.’ It appears by a letter to his brother-in-law (Lord Leicester) that he had most gloomy forebodings as to the result of the enterprise, which, ‘it grieves my soul to be involved in.’ An incident occurred shortly afterwards, which does not redound to the credit of the Earl of Northumberland.
We will give an abridged account of Lord Clarendon’s version. Henry Percy, a zealous Royalist, brother to the Earl of Northumberland, was on his way to France, on the King’s service, just at the time that the Commons had petitioned Charles to prohibit any of his servants leaving England. Striving to embark, he was attacked and wounded by the people of the Sussex coast, and narrowly escaped with his life to a place of concealment, whence he wrote to his brother in a private and confidential manner. Northumberland carried the letter to the House of Commons (which had already voted an impeachment of high treason against Henry Percy), and laid the document upon the table. Clarendon makes but a lame defence for this conduct on the part of the elder brother, who was, he said, ‘in great trouble how to send Henry in safety beyond seas, when his wound was cured, he having taken shelter at Northumberland House.’
But the end of the matter was, that Henry did escape from England, and there was enmity between the brethren from that day forth. This was the first time in which Northumberland ‘showed his defection from the King’s cause, and Charles had been a good friend to him, and laden him with bounties.’
He acted in direct opposition to the King’s commands, when he obeyed those of the Parliament, to equip the royal navy, and to appoint the Earl of Warwick Admiral of the fleet.
In 1642 he resigned his commission of Lord High Admiral, and openly abandoned his allegiance, siding with the Parliamentarians, and though their faith was rather shaken in him on one occasion, he was too valuable an ally to quarrel with.
Northumberland was appointed head of the Commissioners employed to negotiate with the King, in the several treaties of Oxford, Uxbridge, etc., and was intrusted with the custody of the royal children, which he retained until the King’s death. It would appear that he had at least the grace to facilitate their interviews with their unhappy and loving father, and that he cared for the wellbeing of his royal wards. They were subsequently committed to the guardianship of his sister, the Countess of Leicester, and were removed to her Lord’s house of Penshurst in Kent.
Words, in truth, Lord Northumberland used to prevent the execution of the King, but his deeds had hastened the catastrophe. We are told he ‘detested the murder.’ Immediately after Charles’s death Northumberland repaired to his seat at Petworth, in Sussex, where he remained until 1660, when he joined Monck in his exertions to bring about the Restoration. He held no public office under Charles II. excepting the Lord Lieutenancies of Sussex and Northumberland. Clarendon, in a long character of him, says: ‘His temper and reservedness in discourse got him the reputation of a wise man. In his own family no one was ever more absolutely obeyed, or had fewer idle words to answer for;’ and, alluding to his defection from the Royal cause: ‘After he was first prevailed upon not to do that which in honour and gratitude he was obliged to, he was with the more facility led to concur in what in duty and fidelity he ought not to have done, and so he concurred in all the counsels which produced the rebellion, and stayed with them to support it.’