In the 11th century the Spanish Church was required to abandon the Mozarabic liturgy in favour of Roman texts. Walker examines the effect of this change by looking at liturgical manuscripts contemporary with this upheaval, in particular the Silos corpus in the British Library and three missals from Spanish libraries, including the notable Missal of San Facundo. By analysing content, presentation and style, she builds up a series of snap-shots of the textual and visual strategies employed in implementing liturgical change.