The work of Peter Oliver cannot readily be distinguished from that of the father, save for the signature, and is as worthy of praise in every respect, even if it is not more so. That of the father is a little sterner and more forcible than the work of the son, but Peter Oliver is not only known by his delightful miniatures, but also by the copies in miniature size and style which he prepared for Charles I., and which represented some of the great pictures in the King's collection. Several of these copies still remain at Windsor Castle, others are scattered in various collections, and in some instances they are of peculiar importance. For example, there is one in Mr. Pierpont Morgan's collection, representing the marriage of St. Catherine, by a Venetian painter, probably Titian or Palma Vecchio, which is apparently the only record of a vanished painting at one time in the King's collection, but later on sold into Spain, and which there perished in a fire at Seville.
A curious story is told by Horace Walpole concerning some miniatures by Peter Oliver. He says that Vertue handed down the information that Charles II. being very anxious to re-purchase the portraits which had been dispersed on the execution of his father, was told that the widow of Peter Oliver had taken back some of the miniatures, and had them in her possession. The King went to Isleworth to see her, disguising himself that he should not be known, and she showed him several works by her husband. He was pleased with them and tried to purchase them, but the lady stated that she was anxious to submit them to the King, and if he did not buy them, a price should be named for their disposal. The King then discovered himself to her, and at once she showed him many more miniatures which she had not shown to anyone else, and King Charles desired to acquire them all. She would not, however, quote a price to him, but promised to look over her husband's books, and let His Majesty know what prices had been paid to Peter Oliver by Charles I. The King took away the miniatures with him, and afterwards sent one of the grooms of the bedchamber to Mrs. Oliver, offering her a thousand pounds for them, or an annuity of £300 for her life. She chose the latter, but after some few years, hearing that a great many of the miniatures had passed out of the King's possession, and had been given by him to the various ladies at the Court, Mrs. Oliver, who was given to express herself in somewhat blunt language, said that if she had thought the King would have given the miniatures to his mistresses and illegitimate children he should never have had them. Her remark, which was couched in very strong language, was carried by someone to the Court. The poor woman's annuity was at once stopped, and she never again received it.