Physician Theodore Diodati was born in Geneva on 23 August 1573. His was father was a merchant banker of Lucca, where the family had been prominent in public life. Converted to Calvinism he had settled in Geneva by 1567. Theodore studied medicine in Leiden where he matriculated in August 1594. He remained there until 1598, at which time he accepted employment in England as a tutor to the son of John Harington of Exton which brought him in contact with the court of James I. Diodati was both tutor and physician to the Royal children in 1609. By this time he had his own house in Brentford, Middlesex. He later became an intimate friend of John Milton.
Diodati’s medical practice prospered, but his relationship with the College of Physicians was bad-tempered. In numerous controversies, he was supported by the Royal physician Theodore Turquet de Mayerne. Born in Geneva in 1573 within a month of each other, they both descended from Italian Protestant families. A census of strangers residing in London found Diodati and his family in the parish of St Mary Magdalen in September 1618. A similar census placed him in Christchurch and St Faith’s under St Paul’s parishes in 1625. He was still in London in 1630 with a growing number of patients among the gentry. During the following decade he was employed at a number of estates and his traces are much more difficult to locate. He returned to London in 1641 where he took up residency in the parish of St Bartholomew by the Exchange. There he died in the winter of 1651.