The British R.23X class of rigid airships were developed during World War I using the experiences gained from the 23 class, but only two of the planned four R.23X class were built: R.27 and R.29. Both were completed mid-1918, but just two-and-a-half months after entering service R.27 was destroyed by fire in a hangar; while R.29 went on to become the most successful British wartime rigid airship, being the only one to meet enemy action, as well as the only one to sink a submarine.