Professor David Daube suggested in "The Oxford Magazine" of 16 February 1956 that Humpty Dumpty was a "tortoise" siege engine, an armoured frame, used unsuccessfully to approach the walls of the Parliamentary-held city of Gloucester in 1643 during the Siege of Gloucester in the English Civil War. This was on the basis of a contemporary account of the attack, but without evidence that the rhyme was connected. The theory was part of an anonymous series of articles on the origin of nursery rhymes and was widely acclaimed in academia, but it was derided by others as "ingenuity for ingenuity's sake" and declared to be a spoof. The link was nevertheless popularised by a children's opera "All the King's Men" by Richard Rodney Bennett, first performed in 1969.