In 1651 he was at Worcester, meeting with Charles II of England, and receiving tokens of his favour; and like his brother he was a royalist supporter.
Here he was joined by his brother John, who daily read the proscribed service of the Church of England in the presence of a few royalists.
About this time Peter married a Mrs. Sayon, a merchant's widow and a kinswoman of Archbishop William Laud.
At the Restoration, he was made one of the king's physicians in ordinary, and was known in his profession particularly for his treatment of smallpox and all sorts of fevers.
Though the plague could not drive him from his home, the Great Fire of London did in 1666: his house was burned down with St Paul's, and he moved to the neighbourhood of Westminster Abbey.
On 14 Jan 1678 at Westminster Abbey, Mary married Ralph Dutton (1630-1720), who later that same year was created a baronet by Charles II (on 20 Jun 1678).