 He was succeeded by his nephew, Dr. Peter Chamberlen (barbers-surgeons were not Doctors in the sense of physician), as royal obstetrician.The success of this dynasty of obstetricians with the Royal family and high nobles was related in part to the use of this "secret" instrument allowing delivery of a live child in difficult cases.In fact, the instrument was kept secret for 150 years by the Chamberlen family, although there is evidence for its presence as far back as 1634.