He now obtained "a sufficient practice upon the worst of diseases", and remained at Bristol till 8 June 1669, when he was summoned to Newhall in Essex to attend George Monck, Duke of Albemarle, for dropsy.

On 12 July Monck gave him a certificate of his cure, and Charles II, on 6 August, sent letters to the University of Cambridge requesting them to grant Sermon a medical degree.

[2] In 1672 appeared the eighth edition of Sermon's Advertisement concerning those most famous and safe cathartiques and diuretique Pills … wherewith was cured the late Lord-general Monck of the Dropsie.

[c][3] Much of the book is repeated in The Ladies Companion, or the English Midwife (1671, 8vo), which is illustrated with sixteen copper cuts, giving "the various forms of the childs proceeding forth of the womb".

[3] A third work, issued in 1673, was A Friend to the Sick, or the honest English Man's preservative … with a particular discourse of the Dropsie, scurvie, and yellow jaundice.