In July 1629 he lent to Oliver St John the manuscript tract on the bridling of parliaments, written in 1612 by Sir Robert Dudley, titular duke of Northumberland. The tract was secretly circulated by St. John among the parliamentary leaders; Charles I and his ministers were roused, and James, with Cotton and others, was imprisoned by order of the privy council in the autumn of 1629. He was probably released, with the other defendants, on the birth of the Prince of Wales, 29 May 1630.