Cockayne belonged to a cadet branch of a family settled at Ashbourne in Derbyshire since the twelfth century, whose parliamentary record stretched back at least to 1332. His grandfather was a London merchant, and his father, described by James Whitelocke* as ‘rich William Cockayne’ and notorious chiefly as author of the unsuccessful project to supplant the Merchant Adventurers in the export of cloth, was the greatest merchant-financier of his day and first governor of the London plantation in Ulster. Cockayne’s inheritance is said to have consisted of rents amounting to £12,000 p.a., although by his father’s will only £1,500 p.a. came into his immediate possession, the rest being left to his mother who married Henry Carey*, 1st earl of Dover, and survived until 1649.
Having been admitted to the Inner Temple in 1623, Cockayne continued to participate in the social life of the Inn until his death, regularly serving as an officer at the Christmas festivities. He settled into the lifestyle of the country gentry at Rushton Hall in Northamptonshire, which his father had purchased in 1619, and in 1627 he married one of the nieces of his Northamptonshire neighbour Sir Barnabas O’Brien, later 6th earl of Thomond. The marriage was challenged on the ground of a previous alliance between Cockayne and a certain Gertrude Wagstaffe, but a commission of inquiry rejected the objection.
In 1627 Cockayne was joined, as his father’s heir, in a new lease of the customs farm. Apparently under pressure from Buckingham to buy a peerage, he replied in an undated letter that he was too poor to pay for an English viscountcy, having had so many expenses and ‘mulcts of monies’ for the king, and being obliged to find portions (set by his father at £5,000 apiece) for his unmarried sisters. He begged the duke to authorize the payment from the customs of a Crown debt to Thomond of £8,500, which sum had been assigned to Cockayne as his wife’s dowry. He also offered to borrow thereon for the duke’s ‘present occasions’ and even to lend him his sisters’ money ‘in some £20,000 to do you service two years gratis’. Buckingham’s response is unknown.
In 1628 Cockayne was returned for Reigate, probably thanks to his brother-in-law, Sir Charles Howard*, 2nd earl of Nottingham, whose stepmother had a life interest in the moiety of the manor of Reigate. However, he left no mark on the records of the Parliament.
At the outbreak of the Civil War Cockayne was appointed to the Northamptonshire commission of array, and made some effort to put it into execution. He was also created an Irish viscount, doubtless less in recognition of his loyalty than in return for the first of his contributions to the royal cause, said to have totalled over £50,000.
