The church of Greyfriars is a simple aisled nave of eight bays; the style is Survival Gothic fused with Baroque elements. The church initially consisted of six bays and a west tower. After the explosion of 1718 destroyed the tower, Alexander McGill added two new bays and a Palladian north porch to create one building divided into two churches of four bays each. After it was gutted by fire in 1845, David Cousin rebuilt Old Greyfriars with an open, un-aisled interior. Between 1932 and 1938, the interior and arcades were restored by Henry F. Kerr. Notable features of the church include historic stained glass windows by James Ballantine; the 17th century monument to Margaret, Lady Yester; and an original copy of the National Covenant of 1638.