The posthumous son of a minor Hertfordshire gentleman, Mynne was bequeathed a patrimony of just 100 marks, and accordingly sought to make his fortune through trade.
Mynne sat for Old Sarum in the 1621 Parliament as the nominee of the 2nd earl of Salisbury (William Cecil, Viscount Cranborne*).
In his official capacity, Mynne recommended on 1 May that Sir George Marshall* should deliver up any writs of execution that he had obtained in connection with his legal battle to recover money owed to him for procuring a knighthood of the Bath. Two days’ later, he urged that the bill against excessive official charges in the courts should also address lawyers’ fees.
In February 1622 Mynne finally secured increases in the fees that he could charge as clerk of the hanaper, albeit not on the scale that he had hoped.
Through his membership of the Mineral Company, Mynne had made the acquaintance of the 3rd earl of Pembroke, one of the governors, who provided him with a Commons’ seat at West Looe in 1624.
In March 1624 Calvert put pressure on the East India Company to allow Mynne to sell in London a quantity of calico that he had acquired for export purposes. Permission was not granted, but the sale went ahead regardless. This was Calvert’s last known intervention on his brother-in-law’s behalf; early the next year he resigned as secretary of state, and withdrew from active politics. Mynne felt the loss of his patron almost immediately. In January 1625 the long-sought madder patent was awarded to a commercial rival, and in the following June the partnership with Bedford was dissolved.
In fact, the main focus of Mynne’s business activities had already shifted from trade into industry. From May 1627 he was joint lessee of the Mineral and Battery Company’s wireworks at Tintern, Monmouthshire. In December of that year the earl of Pembroke obtained a grant of the Crown’s ironworks in the forest of Dean, and promptly transferred it to Mynne and Sir Basil Brooke, another deputy governor of the Company, in return for an annual rent of £600. Initially all went well, though Pembroke’s death in 1630 deprived Mynne of his last significant patron.
Meanwhile, Mynne had also suffered further setbacks closer to home. In 1633 he was twice hauled before the Admiralty commission for refusing to allow saltpetre men to dig on his Surrey properties.
Following the outbreak of the Civil War, Mynne initially sided with Parliament, and in December 1642 he sought to recover control of the hanaper office. However, Young ignored the suit brought against him in King’s Bench, on the grounds that he was a royal servant, and Mynne’s efforts to circumvent that obstacle apparently ended in failure.
