He was introduced to King James I and VI of England and Scotland by Lord Northampton, and entered the Royal service in 1605.

Cranfield was appointed Receiver-General of rents and revenues from royal lands in Dorset and Somerset by letters patent in 1605.

Much of the work was done by Randolph Baron, Sheriff of Bath, who served as deputy collector, and by clerks employed in London.

As Keeper of the Wardrobe he supervised the spending of £20,000 on the funeral of Anne of Denmark and made an inventory of her jewels.

Cranfield lost his positions and influence shortly afterwards because he opposed the projected war with Spain, and had incurred the hostility of the Prince of Wales and the Duke of Buckingham.

Cranfield's homes included Chelsea House, which he bought in 1619 and improved employing the services of Inigo Jones and Nicholas Stone, and Copthall in Essex.

These included a suite of furnishings for Anne Brett's "lying-in" at Chelsea in 1621 with a cradle with a canopy of crimson damask for James Cranfield in 1621.

The 2nd Earl was succeeded by his brother, Lionel, who died without issue in October 1674, thereafter the Earldom of Middlesex and Barony of Cranfield became extinct.