John Robartes, 1st Earl of Radnor (1606-1685) succeeded his father, Richard Robartes, as Baron Robartes of Truro in May1634.
The barony was purchased under compulsion for £10,000 in 1625. The family had amassed great wealth by trading in tin and wool, and in 1620 began building the family seat, Lanhydrock House near Bodmin.
Educated at Exeter College, Oxford, John Robartes fought on the side of the Parliament during the Civil War, being present at the Battle of Edgehill and at the First Battle of Newbury, and was a member of the committee of both kingdoms. He is said to have persuaded the Earl of Essex to make his ill-fated march into Cornwall in 1644; he escaped with the earl from Lostwithiel and was afterwards governor of Plymouth.
f.l.t.r.: The Marquess of Dorset, Earl of Northumberland, Earl of Surrey, Earl of Shrewsbury, Earl of Essex, Earl of Kent, Earl of Derby, Earl of Wiltshire.
An official defining characteristic of an earl still consisted of the receipt of the "third penny", one-third of the revenues of justice of a shire, that later became a fixed sum.
The eldest son of an Earl generally bears the courtesy title of Viscount or Lord; one refers to a younger son of an earl as the Honourable [Forename] [Surname] and to a daughter as Lady [Forename] [Surname] (Lady Diana Spencer furnishing a well-known example).