Yes, Billy answers correctly. BTW, I did not mean to imply I even had a question, but was just curious if all new questions had to come from winning answerers within what appeared to me a rather small group. I thank you for allowing me to post!
Mine was carefully worded because, long before the IJN mounted their 18.1" guns to Yamato and Musashi, HMS Furious was fitted with a single 18" to her aft barbette, and was the only aircraft carrier once fitted with such a massive gun.
According to Nathan Okun's "Navweaps" site, one of the only three British 18" guns produced was mounted aboard the monitor General Wolfe. While it is unclear whether or not Wolfe's gun was the one removed from Furious, the monitor holds the record for the longest hit ever fired from a Royal Navy warship (36,000 yards), although it was against a land target in Belgium.
Based on the above, the British were apparently the only navy ever to successfully score a hit with an 18" gun, against an enemy target. The IJN fired their 18.1" guns at Leyte Gulf but never scored a hit before turning away to evade torpedoes (Yamato). Japanese 18.1" ordnance was also fired against aircraft, but I don't believe these resulted in any direct hits, either (if I'm wrong, I apologize).
Interesting bits of trivia, to be sure--unless they are factually in error.