We know from Sir Christopher Wren's son that the architect had always intended that the interior of his dome be decorated with mosaics:




"For this purpose he had projected to have procured from Italy four of the most eminent artists in that profession; but as this art was a great novelty in England... it did not receive the encouragement it deserved."
- Parentalia




In the event Sir James Thornhill was commissioned to provide monochrome paintings, illustrating the life of St Paul.




This scene represents the incident related in Acts 27, when Paul, just shipwrecked in Malta in the year AD 60, caught hold of a viper which wriggled out of the fire before which they were warming themselves. The local people expected the saint to have fallen down dead:

"Howbeit they looked when he should have swollen, or fallen down suddenly: but after they had looked a great while, and saw no harm come to him, they changed their minds, and said that he was a god."
- Acts 27




It was not until 1864 that the idea of mosaics was again considered - this time for the eight spandrels under the Dome.

Alfred Stevens (creator of the Wellington memorial in the Cathedral) was commissioned to produce designs for the four prophets: Isaiah, Jeremiah, Ezekiel and Daniel. Of the four, only Isaiah was finished by Stevens: a work which is strongly inspired by Michelangelo. The cartoons of the three remaining prophets were completed by W.E.F. Britten after Stevens' death in 1875.




The painter G.F. Watts was approached to provide designs for the remaining four spandrels - representing the four evangelists, the first of which, St Matthew, was completed to Watts' design in 1866. Once again, Britten completed the scheme - this time passing off some of the work as his own, rather than Watts's.




All eight of these mosaics were executed by the Venetian firm of Salviati, with smooth, flat, non-reflective tesserae copying as closely as possible the painted original.




Attempts to replace Thornhill's Dome paintings in the early 1870's with new ones by Burges and Penrose were dropped as too controversial. In 1878 Lord Leighton and Sir Edward Poynter were invited to prepare cartoons for a new scheme. In this example, which shows a segment of the dome, the roundel is by Lord Leighton, while the remainder is by Poynter. This plan, too, came to nothing.




It's not known whether Wren intended that the eight niches in the drum of the Dome should have statues. They remained empty until 1892, when colossal sculptures of the Fathers of the Church were designed for them by C. E. Kempe.




The four quarter-dome mosaics were added to the designs of Richmond, beginning in 1899. They illustrate subjects from Paul's Epistle to the Corinthians. Perhaps the finest of them is the Crucifixion, in which Christ is seen to be crucified not on a cross, but on the Tree of Life itself, whose branches spread to bring good to all nations.

But the public mood had changed since the installation of the Richmond mosaics in the Quire: there was an outcry in the Press against what was considered desecration of the pure classical architecture of Wren. The scheme went no further.