In the later middle ages Cornwall's diversified economy profited the county's lords and commoners alike, linking them into pan-English credit, exchange and personal networks. Cornishmen and women are to be found trading in commodities as diverse as feathers, fish, cloth and, most significantly, tin, with deals of this sort creating much connectivity. Since tin was so valuable, it is small wonder that leading gentlemen from dynasties as diverse as the Bodrugans and the l’Ercedeknes paid coinage duty on hundreds of thousands of pounds (lbs) of the metal in the first half of the fourteenth century alone. In 1306–7 the landed widow Margery Treverbyn presented as much as 15,000 lbs of tin for coinage. Some local proprietors owned the tin workings themselves, among them Sir Richard Sergeaux, who in 1391 jointly held one such site named ‘Tye’. With the absence of urban economic muscle in the county encouraging gentry involvement in this industry, tin could significantly augment local lordly income. By the fifteenth century, however, it was rarer for leading proprietors to engage as directly as this in the tin trade, although men such as John Bolenowe, a gentleman from Camborne, dealt in unspecified ‘merchandise’. Whatever the reasons behind the retreat, Cornish lords perennially enjoyed the prerogative of toll tin and were not above involvement in trade.

Some gentlefolk relied on income from the metal to rise yet higher in the ranks of society, Michael Trenewith the elder and younger amongst them. Both Michaels traded extensively in tin, using the resultant wealth to acquire more expansive estates and lend money to people as diverse as Sir John Hamley and the obscure John Ycca. Although both father and son regularly employed violence to further their positions, a Michael Trenewith still acquired a place on the county bench from 1338 to 1344 and represented Cornwall in parliament. Tinning interests enabled the elder and younger Trenewith to secure for their family a position of prominence in the county for the rest of the century. It is illustrative of this that one Ralph Trenewith is found serving as duchy receiver in the 1370s and making a good marriage, when he acquired the hand of Joan Bodrugan, one of Otto Bodrugan's heiresses.