 By the end of the 1850s, Britain and France were engaged in a naval arms race.A new class of ironclad ships with powerful rifled muzzle loader (RML) guns, exemplified by the British HMS "Warrior" and the French "La Gloire", posed a substantial threat to existing coastal defences.In response, the British government established a Royal Commission on the Defence of the United Kingdom to review the defences and make recommendations on improvements.