His next appointment was Third Sea Lord, the naval officer with overall responsibility for provision of ships and equipment. He presided over the development of torpedo boat destroyers armed with quick-firing small-calibre guns (called destroyers at Fisher's suggestion). A suggestion for the boats was brought to the Admiralty in 1892 by Alfred Yarrow of shipbuilders Thornycroft and Yarrow, who reported that he had obtained plans of new torpedo boats being built by the French, and he could build a faster boat to defend against them. Torpedo boats had become a major threat, as they were cheap but potentially able to sink the largest battleships, and France had built large numbers of them. The first destroyers were considered a success and more were ordered, but Fisher immediately ran into trouble by insisting that all shipbuilders, not just Yarrow's, should be invited to build boats to Yarrow's design. A similar (though opposite) difficulty with vested interests arose over the introduction of water tube boilers into navy ships, which held out the promise of improved fuel efficiency and greater speed. The first examples were used by Thornycroft and Yarrow in 1892, and then were trialled in the gunboat . However, an attempt to specify similar boilers for new cruisers in 1894 led to questions in the House of Commons, and opposition from shipbuilders who did not want to invest in the new technology. The matter continued for several years after Fisher moved on to a new posting, with a parliamentary enquiry rejecting the new boilers. Eventually the new design was adopted, but only after another eighteen ships had been built using the older design, with consequent poorer performance than necessary.