The papers form part of the Royal United Service Institution collection transferred to the Museum in 1968. There are logs, 1776 to 1778, 1782 to 1784, 1786 to 1790, 1793 to 1795 and 1799 to 1801; a diary for 1786; mathematical work books and a sketch book. The loose papers include a biographical memoir, letters by Riou to his family, his own correspondence, papers relating to his voyage in the Guardian and notes on the trials of the mutineers of 1797.

Administrative / biographical background
Riou entered the Navy in 1774, first joining the Barfleur at Portsmouth. He served in the Romney on the Newfoundland Station, 1775 to 1776, when he sailed in the Discovery on Cook's third voyage. On his return home in 1780 he was promoted to lieutenant and appointed to the Scourge in the West Indies, where he stayed until 1782. He then served in the Mediator in the Channel from 1782 to 1783 and in the Ganges, guardship, from 1783 to 1784. Riou was then on half-pay for two years. In 1786 he travelled on the continent. Later in the year he was appointed to the Salisbury, Newfoundland, serving there until 1788. In 1789 he was appointed to command the Guardian, carrying convicts and stores to Australia. The ship struck an iceberg and was badly damaged but Riou managed to sail her back to the Cape of Good Hope. He returned home in the Sphinx in 1791 and was promoted to commander and to captain within the year. From 1793 to 1795 he commanded the Rose and Beaulieu in the West Indies but was invalided home in 1795 and appointed to command the Princess Augusta, Royal Yacht. He served on the courts martial following the mutiny of 1797. In 1799 he commissioned the Amazon and in 1801 went with the Baltic Fleet where he was killed at the battle of Copenhagen.