It is well to bear in mind the following facts with reference to the dedications of churches. Their consecration was formalised into a definite ceremony in the time of Constantine the Great (d. 337), and the custom of distinguishing them by special names then became universal, although evidences of the custom exist nearly a century earlier. Founders of churches desired to place their foundations under the protection of some saint, and worshippers in these churches in later times added in gratitude after the name of the saint, the name of the founder, to keep it in perpetual remembrance. The rebuilding of a church was sometimes made the occasion, at the re-consecration, of a change of name, so that in 816 Archbishop Wulfred ordered that on or by every Altar an inscription should be set up recording its dedication name.If this canon had been observed many original dedications might have been preserved, but it appears to have been greatly neglected. In early times the designation "Saint" seems to have been bestowed on individuals of conspicuous holiness by the Christian community to which he or she belonged, and not necessarily by the Pope or even by a bishop in the first instance. This accounts for the large number of more or less obscure persons so distinguished in ecclesiastical nomenclature. It appears from the letters of St. Cyprian that this practice was open to abuse, and that the bishops considered it necessary to use caution in order to guard against the recognition of undeserving persons. It was not until the 12th century that the Pope reserved to himself the right to add to the roll of saints and that a regular form of procedure was established in the Roman Courts to test and to pronounce on the title of persons to the public esteem of the church, 1170. The earliest instance of the issue of a solemn decree of canonisation is by Ulric, Bishop of Augsburg, 993.
Frequent instances of double dedications occur in London and elsewhere, and these may arise in four ways : (1) From the original intention of the founder, who may have desired for special reasons to place his church under the particular guardianship of more than one saint. (2) The natural tendency above mentioned to associate the founder's name with that of the saint whom he had himself chosen. (3) The practice of re-dedicating churches under some new name and making use of both of the old and of the new dedications. (4) The union or consolidation of two previously distinct parishes.
After the Reformation in the time of Henry VIII., there were many changes in dedications, the tendency being to restrict dedications to the Apostles of our Lord, to the Blessed Trinity, or to the Blessed Saviour. The dedications of many churches to St. Thomas of Canterbury were changed at that time to St. Thomas the Apostle.
The dedications chosen for churches in London in early times are attributable to three influences, Saxon, Danish, French ; such names as St. Ethelburga, St. Etheldreda suggest Saxon influence. St. Olave, St. Magnus, seem to be attributable to Danish influence. St. Mary Magdalene, St. Stephen, St. Vedast to the Norman Conquest, introducing French influence.
Another interesting fact calls for attention in connection with the dedications of churches in early times to the Holy Trinity. Several instances occur of the dedication of churches to the Holy Trinity and to our Saviour Christ, so that the designations are used interchangeably to denote the same church. Thus the Priory of Holy Trinity, Aldgate, is frequently referred to as Christ Church Priory. Christ Church, Canterbury Cathedral, is also designated the church of the Holy Trinity. Christ Church in Hampshire was originally dedicated to the Holy Trinity, but being rebuilt by Flambard, temp. Wm. II., was rededicated to "Our Saviour Christ."