King's College Chapel is an exceptional structure, not only in its physical form, but in the architectural ideals that manifest throughout. Of particular interest in the chapel is the great fan vault and the circumstances in which it may have been constructed. There is considerable evidence suggesting that the fan vault of King's College Chapel was not part of the original design. Two primary historians, Robert Willis and Francis Woodman, have conducted thorough research into the matter and have produced several theories as to the nature of the vault. The argument for an alteration of the original design during construction can be seen through observational, structural, and formal analysis.