IN LATE MEDIEVAL ENGLAND, royal ships were the personal property of the king, and their numbers fluctuated markedly over time. A royal navy did not exist as such and vessels were often disposed of to pay debts, as occurred after the death of Edward III in 1377. The construction and maintenance of vessels in the king's fleet were the responsibility of an official known as the clerk or keeper of the king's ships. His duties included the construction, repair, victualling and safe keeping of the royal ships. He was not responsible, however, for the vessels whilst they served in naval operations, which instead were transferred to admirals whose expenses were paid for by treasurers of war. The numbers of royal vessels varied over time, for instance twenty-seven ships were at sea in 1370, twenty in 1372 and thirteen in 1374. These ships only comprised a small proportion of the vessels used in naval expeditions, as the vast majority of ships used were hired or impressed merchant ships. Nevertheless, royal ships served an important role as warships, troop transports and as ships for diplomatic missions. The armament of these vessels changed considerably over the course of the fifteenth century. Henry V's great ship, the Grace Dieu of 1,400 tons, completed in 1420, was the largest royal vessel constructed before the seventeenth century, yet it only possessed three guns. By contrast, Henry VII's slightly smaller ship, the Regent of 1,000 tons, was equipped with a total of 225 guns for an expedition to Scotland in 1497. The intervening seventy-seven years had therefore witnessed a significant change in the use of artillery in naval warfare. This chapter traces how and why this development occurred.

The principal source for the study of royal ships is the accounts of the keeper of the king's ships, which survive regularly for the years 1327–1452 and after a gap of thirty-two years survive intermittently from 1485 onwards. For the earlier period these exist in enrolled form in the foreign account rolls of the Exchequer. The accounts are in a standard format consisting of: the receipt of money, receipt of ships and equipment, purchases, expenditure of equipment and, finally, the remaining ships and equipment in the possession of the keeper.