The article looks at a case of forensic research in opera. Whittington is an English legend but the composer was French. It was first performed in English in London and then after Offenbach's death - some 20 years later - a French version for Paris was written by Nuitter and Tréfeu. The case in question in this article is to try and identify the original and its translation. Offenbach put music to the French libretto, but looking at the many changes a closer analysis is needed in order to rebuild the original text.