The Iris class comprised two ships, HMS Iris and HMS Mercury, which served with the Royal Navy. They were the Royal Navy's first all steel ships. They were designed as dispatch vessels by William White under the direction of Nathaniel Barnaby but were later re-created as Second Class Cruisers. They were distinguished by their long, slender hulls which were influenced to an unprecedented degree by their machinery. This combination of fine lines and powerful twin Maudslay engines made them the fastest ships of their day, with Mercury attaining 18.6 knots from her 7,735 horsepower. This class re-established the traditional status of cruisers as being the eyes of the fleet - being faster than the contemporary ships of the line.