The church interior is, at 40 feet, the highest of any Wren church. As it was originally surrounded by other buildings, Wren created tall main windows, as well as clerestory windows. The largest window of all was in the East, filling the arched alcove. Early in the 19th century, this was found to be weakening the wall and so was filled in. In 1815, the painting of the Ascension by Andrew Geddes was installed above the reredos in the place previously occupied by the window.