Sir John Robinson, the lieutenant of the Tower, had been one of the judges in the affair of Gracious Street. He had either taken a dislike to Penn, or else was deeply impressed with the conviction that the young Quaker was a peril to the state. Finding that there was to be a meeting in Wheeler Street, at which William was expected, he sent soldiers and had him arrested. They conveyed him to the Tower, where he was examined. "I vow, Mr. Penn," said Sir John, "I am sorry for you; you are an ingenious gentleman, all the world must allow you, and do allow you, that; and you have a plentiful estate; why should you render yourself unhappy by associating with such a simple people?" That was the suspicious fact. Men in Robinson's position could not understand why Penn should join his fortunes with those of people so different from himself, poor, ignorant, and obscure, unless there were some hidden motive. He must be either a political conspirator, or, as many said, a Jesuit in disguise, which amounted to the same thing. "You do nothing," said Sir John, "but stir up the people to sedition." He required him to take an oath "that it is not lawful, upon any pretense whatsoever, to take arms against the king, and that [he] would not endeavour any alteration of government either in church or state." Penn would not swear. He was therefore sentenced for six months to Newgate. "I wish you wiser," said Robinson. "And I wish thee better," retorted Penn. "Send a corporal," said the lieutenant, "with a file of musqueteers along with him." "No, no," broke in Penn, "send thy lacquey; I know the way to Newgate." William continued in prison during the entire period of his sentence, at first in a room for which he paid the jailers, then, by his own choice, with his fellow Quakers in the "common stinking jail." Even here, however, he managed, as before, to write; and he must have had access to books, for what he wrote could not have been composed without sight of the authors from whom he quoted. The most important of his writings at this time was "The Great Case of Liberty of Conscience once more briefly Debated and Defended by the Authority of Reason, Scripture and Antiquity." Being released from prison, Penn set out for the Continent, where he traveled in Germany and Holland, holding meetings as opportunity offered, and regaining such strength of body as he may have lost amidst the rigors of confinement.