The murder of the Archbishop of Canterbury Thomas Becket in 1170 at the hands of trusted men of King Henry II of England had a huge impact on twelfth-century Europe. His violent death was the tragic outcome of a far-reaching conflict between the secular power of European feudal monarchies and the spiritual power of the Church. Following the events, the figure of Becket achieved great notoriety and his cult spread everywhere, also in the Iberian Peninsula, where we find texts and works of art commemorating his martyrdom and sanctification, like the wall paintings of Santa Maria de Terrassa (c. 1180). A painted tragedy unfolds the dissemination of the Thomas Becket cult and illustrates the relations between England and the Iberian Peninsula eight hundred and fifty years ago. Why did Ramon Beren-guer IV entrust his children’s guardianship to the King of England? Did Eleanor Plantagenet, daughter of Henry II, play an active role in promoting the Becket cult in the kingdom of Castile? Was the presence of an English canon named Harvey in Santa Maria de Terrassa the driving force behind the Romanesque paintings depicting the martyrdom of Thomas Becket? These are some of the questions of a historical puzzle that took place in Catalonia during the second half of the twelfth century.