The original intention was to complete the building as a cross church, with choir, nave, and transepts, but the choir only has been completed. The transepts have been partly erected, the east wall being carried up to a considerable height, but the nave has not been erected. The church consists of a choir, with north and south aisles, connected by an aisle which runs across the east end, giving access to a series of four chapels beyond it to the east. Beyond the east end of the church, and on a lower level, to suit the slope of the ground, a chapel has been erected that is reached from the south aisle by a stair. It is barrel-vaulted and is lighted by an eastern window. There are ambries in the walls and an eastern altar with a piscina. There are also a fireplace and a small closet on the north side. On the south a door leads to what has been an open court, where there are indications of other buildings having existed or being intended. In all probability there was a residence here, and the chapel may have served both as sacristy and private chapel. This chapel was probably built by the liberality of Lady Douglas, Sir William St. Clair's first wife. The church is profusely adorned with sculpture which generally represents Scripture scenes, and one of the most curious examples in the remarkable decoration of the edifice is the ornamentation of the south pillar of the east aisle, known as the "Prentice Pillar"--named by Slezer (1693) as the "Prince's Pillar" and by Defoe (1723) the "Princess's Pillar." It consists of a series of wreaths twisted round the shaft, each wreath curving from base to capital round one quarter of the pillar. The ornamentation of the wreaths corresponds in character with the other carving of the church, and the grotesque animals on the base find a counterpart in those of the chapter-house pillar at Glasgow Cathedral. At the Reformation the lands and revenue of the church were virtually taken away, and in 1572 they were relinquished by a formal deed of resignation. The chapel does not seem to have suffered much violence till 1688, when a mob did much mischief. It remained uncared for, and gradually became ruinous till the middle of the eighteenth century, when General St. Clair glazed the windows, relaid the floor, renewed the roof, and built the wall round about. Further repairs were executed by the first Earl of Rosslyn, and again by the third Earl, who spent L3000 principally in renewing and retouching the carvings of the Lady Chapel--a work said to have been suggested by the Queen, who visited the church in 1842. Since 1862, services in connection with the Scottish Episcopal Church have been held within it. At the west end a vestry and organ-chamber were erected a few years ago.