Two of the letters cover unsuccessful British attempts to capture Ferrol and Cadiz from the Spanish in August and October 1800, led by Lieutenant General James Pulteney and Sir Ralph Abercromby respectively. Pulteney was censured by the House of Commons for failing to attack Ferrol after examining the fortifications and judging that the fortifications and Spanish garrison were too strong; Abercromby had retired from a joint army and navy attack on Cadiz when he felt the landings were too slow. In the sections of the letters provided Popham offers a reserved defence of Pulteney. Popham had served with the Pulteney and Abercromby in the ignominious expedition to the Helder peninsula in the summer of 1799, and was therefore well placed to offer his opinion on their conduct.

The remaining five letters concern Popham’s signalling system, developed in 1800, which enabled captains to communicate much more effectively by providing both an alphabet and a large vocabulary of signals (in contrast to the limited signals proscribed in the Fighting Instructions which were previously in use). The letters contain endorsements for the system from three naval officers and the Secretary of War William Huskisson. These complement the Library’s existing strong holdings of signal books and are important to our understanding of the evolution of marine technology.