John Reresby's Diary is in Stewart Books.
5th August 1665. His royal highness [aged 31] and his duchess [aged 28] came down to York, where they stayed till September the 23rd, when the Duke went for Oxford, where the King [aged 35] was to meet the Parliament. The Duchess went not till some time after. Most of the gentry attended at York whilst their liighnesses were there. The Duke passed his time in shooting and other exercises, the Duchess in receiving the ladies, which she did very obligingly. One evening having a little snake (which I kept in bran in a box) in my hand as I was in the presence, one of the maids of honour seeing of it was frightened. The Duchess, hearing the noise, and what was the occasion, desired to see the snake, and took it into her hand without any fear. This Duchess was Chancellor Hyde's [aged 56] daughter, and she was a very handsome woman, and had a great deal of wit; therefore it was not without reason that Mr. Sydney [aged 24], the handsomest youth of his time, of the Duke's bedchamber, was so much in love with her, as appeared to us all, and the Duchess not unkind to him, but very innocently. He was afterwards banished the Court for another reason, as was reported.
5th August 1665. The Duchess [aged 28] in her return lay at Welbeck [Map], the old Duke of Newcastle [aged 72] being alive, where she was splendidly entertained, the Duke of York [aged 31] having directed that the same respect should be paid her wherever she passed as if he were present. The Duke of Buckingham [aged 37] and my Lord Ogle [aged 35] had a quarrel there.
Samuel Pepys' Diary. 9th January 1666. After dinner Pierce and I up to my chamber, where he tells me how a great difference hath been between the Duke [aged 32] and Duchesse [aged 28], he suspecting her to be naught with Mr. Sidney [aged 24]1. But some way or other the matter is made up; but he was banished the Court, and the Duke for many days did not speak to the Duchesse at all. He tells me that my Lord Sandwich [aged 40] is lost there at Court, though the King [aged 35] is particularly his friend. But people do speak every where slightly of him; which is a sad story to me, but I hope it may be better again. And that Sir G. Carteret [aged 56] is neglected, and hath great enemies at work against him. That matters must needs go bad, while all the town, and every boy in the streete, openly cries, "the King cannot go away till my Baroness Castlemaine's [aged 25] be ready to come along with him"; she being lately put to bed And that he visits her and Mrs. Stewart [aged 18] every morning before he eats his breakfast. All this put together makes me very sad, but yet I hope I shall do pretty well among them for all this, by my not meddling with either of their matters. He and Ferrers gone I paid uncle Thomas his last quarter's money, and then comes Mr. Gawden and he and I talked above stairs together a good while about his business, and to my great joy got him to declare that of the £500 he did give me the other day, none of it was for my Treasurershipp for Tangier [Map] (I first telling him how matters stand between Povy [aged 52] and I, that he was to have half of whatever was coming to me by that office), and that he will gratify me at 2 per cent. for that when he next receives any money. So there is £80 due to me more than I thought of. He gone I with a glad heart to the office to write, my letters and so home to supper and bed, my wife mighty full of her worke she hath to do in furnishing her bedchamber.
Note 1. "This Duchess was Chancellor Hyde's [aged 56] daughter, and she was a very handsome woman, and had a great deal of wit; therefore it was not without reason that Mr. Sydney, the handsomest youth of his time, of the Duke's bedchamber, was so much in love with her, as appeared to us all, and the Duchess not unkind to him, but very innocently. He was afterwards banished the Court for another reason, as was reported" (Sir John Reresby's Memoirs, August 5th, 1664, ed. Cartwright, pp. 64,65). "'How could the Duke of York make my mother a Papist?' said the Princess Mary to Dr. Bumet. 'The Duke caught a man in bed with her,' said the Doctor, 'and then had power to make her do anything.' The Prince, who sat by the fire, said, 'Pray, madam, ask the Doctor a few more questions'" (Spence's "Anecdotes", ed. Singer, 329).