Both Explorer and Excalibur were fitted with the latest submarine escape arrangements, including the one-man chamber, and equipped with the most modern escape breathing apparatus for use by the ship's company in the event of an emergency.
Explorer and Excalibur were, not unnaturally, known as the 'blonde' submarines, because of their peroxide fuel, and they served a useful purpose inasmuch as they gave the Royal Navy's anti-submarine forces some valuable practice against fast targets. Their main use, however, was to prove that the HTP system did not represent the way forward for RN submarine development. Indeed, HTP proved difficult to the point of being dangerous, and there was more than one contemporary report of explosions
