He inherited the Dukedom of Lennox on his father's death in 1624 and in 1625, at the age of 13, was made a Gentleman of the Bedchamber to the newly crowned King Charles I, who knighted him on 29 June 1630 and invested him as a knight of Order of the Garter in 1633.
Dukedom of Richmond
The Earldom of Richmond had become absorbed into the crown in 1485 when Henry Tudor, Earl of Richmond, became King Henry VII. The Scottish connection to the Richmond title began in 1613 when James Stewart's uncle Ludovic Stewart, 2nd Duke of Lennox (1574–1624), was created by King James I as Earl of Richmond and was later, in 1623, created by the same king Duke of Richmond and Earl of Newcastle.[2] However he died childless a year later when all his titles (excepting those inherited from his father, namely Duke and Earl of Lennox) became extinct. On 21 August 1637 he was created the 3rd Baron Clifton via his mother.[3]
The title Duke of Richmond was re-created in 1641[2] by King Charles I for Ludovic's nephew and eventual heir James Stewart, 4th Duke of Lennox, who was also granted Cobham Hall and the manor of Cobham, Kent, which became his main residence.