All hail, mysterious King. P. Doddridge. [Christ the King.] This hymn on Rev. xxii. 16 is not in the “D. MSS." It was first published (posthumously) in his Hymns, &c, 1755 No. 359, in 4 stanzas of 4 lines, and entitled "Christ the Root and Offspring of David, and the Morning Star." It is also repeated in later editions of the same work, and in the corrected and enlarged ed. by J. D. Humphreys, 1839. Its use in Great Britain is limited, and confined almost exclusively to the older collections; but in America it is given in several hymnals.
-- John Julian, Dictionary of Hymnology (1907)