One of the leading merchants in late 14th-century Hull, Fountenay first appears in 1382, when he exported a modest consignment of cloth. The local customs accounts for the next two decades show that he maintained a regular interest in the cloth trade, while also dealing in commodities as diverse as wine, herring and iron, all of which he bought and sold in relatively large quantities. By July 1387 he was sufficiently well established to join with four other shipowners, including William Terry, in providing a large vessel, a barge and a balinger of war, ‘arrayed and equipped for the safe passage and return of fishmongers, merchants and other the King’s lieges at sea in the northern parts ... and for the destruction of the King’s enemies of France and Scotland on the sea coast.’
Meanwhile, on three occasions between July 1397 and August 1401, Fountenay’s name was put forward for jury service at assizes in Hull, although he was selected only once. It seems likely that the general pardon issued to him by Richard II in July 1398 was little more than a formality, since unlike many of the other prominent local burgesses he is not known to have engaged either in acts of privacy or evasion of customs dues. Indeed, comparatively little evidence survives about his personal affairs. The property in Mytongate which he acquired in December 1397 was quite possibly that which descended after his death to his widow, Ellen, and their daughter, Elizabeth, and which they themselves disposed of in February 1424; but it looks very much as if his interest in other conveyances of land in Hull was simply that of a trustee. He last appears in August 1416, and was certainly dead by June 1418, when the above-mentioned pardon for outlawry was accorded to ‘Thomas Fountenay, late burgess and merchant of Kingston-upon-Hull’. The William Fountenay of Hull who was licensed to export grain from the port in 1428 may perhaps have been his son.