Vatican cod. gr. 1851 is composed of four bifolia, which contain the partial text of a poem and seven illuminations. The protagonists described in the poem are a Byzantine emperor, his youthful son, his daughter and a young foreign princess to whom the son is betrothed. Comparisons with other examples of imperial dress lead to the conclusion that the illustrations in the manuscript are probably fourteenth-century. I propose that the groom was Andronikos IV, who married, in 1356, aged eight, Maria, the nine-year-old daughter of the tsar of Bulgaria, Ivan Alexander. This marriage raises issues of children’s roles at court and the nature of books made for them.