Mohun’s mother died while he was still a child, and relations with his stepmother were strained. He attended Oxford with his elder half-brother William, and in 1611 progressed to the Middle Temple, where he was bound with Francis Courtney* and Jonathan Rashleigh*. Mohun enjoyed close ties with his mother’s family, the Heles, and was named as a trustee of their estates in an abortive private bill in the 1614 Parliament.
Of the two men, Mohun seems to have been the more aggressive litigant, initiating a string of suits against not just his father, but also Sir Reginald’s relatives and associates. One of the latter, Sir Thomas Monck*, complained in a 1619 case concerned with an unredeemed bond, that Mohun had extorted repayments from him on account of his friendship with Sir Reginald, even though Monck had provided collateral security only, and was not the principal debtor.
In 1622 a number of the Mohun lawsuits came to court, and an accommodation between the parties was finally reached. Accordingly a fresh bill was prepared for the next Parliament, to be presented with a public show of reconciliation. Probably as one element of this, Mohun himself was returned to the Commons for the first time in 1624, as a Member for Grampound. The borough lay just a few miles from Penwarne, but significantly one of the biggest landowners in the district was Sir Reginald’s brother William, who had been party to the baronet’s obstructive conveyances.
In 1625 Mohun was again returned for Grampound, where he strengthened his position as patron. The borough initially offered the second place to another Cornish gentleman, Sir Richard Edgcumbe, who had sat there in 1624, but ultimately dropped him in favour of Sir Samuel Rolle, Mohun’s cousin through the Hele line. At West Looe, Mohun provided a seat for his associate Edward Thomas, probably with the assistance of his brother-in-law John Trelawny, the borough’s steward. East Looe, where Sir Reginald was recorder, returned (Sir) James Bagg II, who was almost certainly already on close terms with Mohun but may have had independent means of obtaining a place there. No record now survives of Mohun’s contribution to the Parliament’s proceedings.
The resolution of the family feud was accompanied by Mohun’s entry into Cornish administration. He became a j.p. in May 1625, and was acting as a deputy lieutenant by July of the following year. This was a critical moment for the county’s political structures. The duchy of Cornwall’s local administration was controlled by the lord warden of the stannaries, the 3rd earl of Pembroke. In the aftermath of the 1626 Parliament, in which Mohun provided a Grampound seat for Edward Thomas, Pembroke was obliged to relinquish much of his influence in the county to his political rival, the duke of Buckingham, leaving prominent Cornish clients such as his vice-warden William Coryton* and (Sir) John Eliot* at the duke’s mercy. In July 1626 both men were removed from the bench, and the process of dismissing Eliot from the vice-admiralty of Devon commenced.
In their attitudes towards local government, Mohun and Bagg seem to have been in broad agreement. In July 1628 Mohun reportedly said that ‘the state could never be well ordered while there were parliaments, because in Parliament every man will have his own fancies and so nothing can be brought into any certainty or settlement by that course’; the Crown should rather commit the direction of local business to ‘select men in every county...[who] by their moving the affairs of the county might thereby better order and dispose them’.
On balance, the evidence assembled by Eliot indicates that stannary justice under Mohun was both more expensive and less reliable than hitherto, and that unrest in Cornwall was mounting by late 1627. Nevertheless, Pembroke remained neutral, at the end of the year effectively surrendering to his vice-warden the authority to summon a stannary convocation, or regulatory assembly, whose membership Mohun promptly attempted to prescribe. Meanwhile, pressure had been maintained on Eliot through the vice-admiralty inquiry, and Bagg could boast to Buckingham that the relatively successful collection of the Forced Loan in the county owed much to the efforts of his own allies. Both Eliot and Coryton had suffered imprisonment for opposing the Loan, and remained in official disgrace.
Mohun, despite his own defeat, was able to nominate Edward Thomas to West Looe once more, and placed at Buckingham’s disposal seats at East and West Looe and Grampound which were filled by William Murray, John Packer and Sir Robert Pye. In his capacity as vice-warden, he may also have found a place at Lostwithiel for the courtier Sir Robert Kerr, replacing him with Sir Thomas Bagehott after Kerr opted to sit elsewhere. However, Bagg was seriously alarmed by Eliot and Coryton’s victory, and on 17 Mar. proposed that the duke should authorize an inquiry into the county election, to be managed by Mohun and his friends. He also revived the idea of granting a peerage to the vice-warden, urging Buckingham on 19 Mar. to ‘take care of’ him.
The period of the 1628-9 Parliament was another climacteric in Cornish politics. Buckingham’s assassination, Eliot’s fatal imprisonment and Coryton’s submission to the king brought a substantial realignment in factional divisions. Mohun, bereft of his principal patron, lost his vice-wardenship late in 1629, though he apparently retained his other offices. Around the same time he again fell out with his father. Sir Reginald, accused of breaching the terms of the 1624 Mohun Act by wasting the Boconnoc estate, denied the charges and maintained that the arguments had stemmed all along from Mohun’s suspicions, rather than more substantial causes.
