He had been in prison for some months when it occurred to him to address a letter to the Protector himself.
"May it please your Highness," it began, "Rulers within the circle of their government have a claim to that which is said of the Deity: they have their centre everywhere and their circumference nowhere, It is in this confidence that I address your Highness, as knowing no place in the nation is so remote as not to share in the ubiquity of your care, no prison so close as to shut me up from the partaking of your influence." After explaining that he had been and still was a Royalist, but that he had taken no active part in affairs for about ten years, he concludes, in a clever vein of compliment, thus: "If you graciously please to extend indulgence to your suppliant in taking me out of this withering durance, you will find mercy will establish you more than power, though all the days of your life were as pregnant with victories as your twice-auspicious Third of September." The appeal to Cromwell's magnanimity was successful.

Cleveland was released, came to London, and lived by his wits there till his death in May 1658.[3]--A much later returner from among the Royalist exiles than either Hobbes or Davenant was the poet COWLEY.

His return was late in 1655 or early in 1656, and seems to have been attended with some mystery.

He had been for years at Paris or St.Germains, in the household of Lord Jermyn, acting as secretary to his Lordship and to Queen Henrietta Maria, deciphering the secret letters that came to them, and therefore at the very heart of the intrigues for Charles II.

Yet, after a temporary imprisonment, security in L1000 had been accepted in his behalf, and he had been allowed to remain in London.
The story afterwards by his Royalist friends was that he had come over, by understanding with Jermyn and the ex-Queen, to watch affairs in their interest and send them intelligence, and that, the better to disguise the design, he pretended compliance with the existing powers, meaning to obtain the degree of M.D.from Oxford, and set up cautiously as a medical practitioner.