Cage chantries were institutions that celebrated masses for the good of the soul of their founder. In late medieval England chantries were the most popular type of religious foundation and could be founded at existing altars, in existing chapels, or involved the building of an external or free-standing chapel. Cage chantries were physically separate chapels erected within existing churches in the period 1366 to 1555. These were erected in cathedrals, collegiate and parish churches. Fifty-four have been positively identified for this study. This group has been examined within both its documentary and physical contexts, as far as evidence allows. These chapels were founded disproportionately in monastic churches, an important factor as so few of these buildings survived the Dissolution of the Monasteries in the 1530s. Therefore these are representative of the others that were most probably founded, but have not survived or been identified. Physically these chapels appear only in churches with a clerestory and at least one aisle. Within these physical constraints, this group has emerged to allow an analysis of the process of foundation not seen in other studies. This process involved not only the endowment or funding arrangements for the celebration of perpetual masses for the soul of the founder, but also an insight into the choices made. The choices for founders included not only the church in which the chapel was located, but also the location within that building. These were small chapels with little room for a congregation, yet proved a popular choice due to the flexibility of their possible locations. Many were close to spiritually significant sites such as shrines or altars or were linked physically to the building projects of their founders. These founders are demonstrated not to endow these chapels in the form described by other chantry studies. A comparison of the process outlined by Kathleen Wood- Legh with the majority of this group has highlighted some of their common features. It is the foundation process and the type of mother house that proscribe the documentary sources available for study. Each cage chantry encapsulates the aspirations of its founder modified by practical considerations, both of space within their mother church and also the permission of these authorities. These were essentially highly personal foundations, located mainly in prestigious churches. While cage chantries are not an aberration of their age, nevertheless as a group they illustrate a flexibility both in the use of physical space and the means of founding a perpetual institution for the benefit of their souls after death that illuminates intercessionary institutions more generally.