Carleton could trace his ancestry back to late-thirteenth-century Yorkshire, but his immediate roots lay in Surrey and Oxfordshire. His paternal grandfather, Anthony Carleton†, a minor official in the queen’s Household, leased the Oxfordshire manor of Baldwin Brightwell from the Crown until the later sixteenth century, when Anthony’s eldest surviving son and heir, George, took up residence at neighbouring Holcombe. At the beginning of James’s reign, George was one of the three surveyors of the Stable,
Following a university education which culminated in the award of his BA, Carleton embarked upon a tour of the Continent. From Naples he travelled to Venice, which he reached in February 1612. There he paid a call on his uncle Sir Dudley Carleton*, the English ambassador, who remarked on his nephew’s capacity for parting with the contents of his purse that ‘if he hold on as he hath begun he will spend as fast as his father will save’.
Carleton probably helped to finance his life of leisure by selling off the lands in Hertfordshire left to him by his maternal grandfather.
No sooner had Parliament assembled than Carleton’s father died.
Carleton helped to compile a report on Cambridgeshire’s militia in November 1628.
Shortly after his uncle’s death, Carleton petitioned the king for a grant of 2,000 acres of drained fenland, which had previously been promised to Dorchester. He claimed that he had given 20 years’ service to the Crown and yet had not been compensated for the loss of an office, by which he may have been referring to his earlier position as one of the king’s equerries.
