Abbey Church and Minor Basilica of St Gregory the Great and the north cloister, Downside Abbey

The Abbey Church and Minor Basilica of St Gregory the Great at Downside Abbey, together with the monastery's north cloister, was designed by the architectural practice Dunn and Hansom and built between 1879 and 1938. Later phases of the work were carried out by architects Thomas Garner, Frederick Walters, and Sir Giles Gilbert Scott. The church remains unfinished at its west end. The building is in the 13th-century French Gothic style, with later phases executed in the Early English, Decorated, and Perpendicular styles. The stained glass is by Hardman and Company, Lavers, Barraud, and Westlake, and Ninian Comper. Architectural carving and fixtures and fittings were created by Alfred B. Wall of Cheltenham, Ninian Comper, Ferdinand Stuflesser, and Edward Carter Preston among others.

The church is built of local lias stone and faced with Bath stone ashlar. The roof is covered with plain clay tiles, while the east-end chapels are roofed in copper sheeting. The principal floors are paved in stone. Windows are of one, two, three, and four lights with varied tracery.

The plan is cruciform and aisled, comprising an eight-bay nave with passage aisles, the crossing, north and south transepts, a seven-bay choir, an ambulatory, radiating chapels, and a crypt beneath the east end. The south transept is screened from the body of the church and forms part of the north cloister of the monastery, with the organ and galleried chapels to the west and east above. To the south of the transept is the tower. To the north is the sacristy.

The temporary west front is built of coursed lias stone in a simplified Perpendicular style, with three tall lancet windows above a relieving Romanesque arch to the west door. There is a two-light window to the gable. The elevation is framed by pilasters with offsets, and to either side are lean-to aisles, with a domestic-scale lean-to porch to the north aisle.

The Perpendicular-style south tower rises to a height of 51 metres. The ordered south door is framed by blind arcading with gabled and crocketed heads, and a decorated tympanum with niches containing three statues carved by R.L. Boulton and Sons of Cheltenham. Above are a pair of narrow lancet windows and a high circular window with curvilinear tracery. The lower stage of the tower is framed by set-back buttresses with offsets and gabled tops. The upper stage narrows as it rises through its three tiers of Y-tracery belfry windows, with the corners of the tower transitioning from octagonal shafts, through castellated towers, to crocketed pinnacles. To either side of the tower is the north cloister of the monastery, with the gallery chapels to the abbey above, and a plain parapet. The bays, three to the left and five to the right, are articulated by pilasters that match those to the tower. Behind and above are the nave, with three-light clerestory windows divided by buttresses with offsets and a parapet above, and the choir which has tall clerestory windows with a dividing transom, separated by flying buttresses. The parapet to the choir has an elongated trefoil design that continues to the east and north elevations.

The east end of the choir is framed by towers with niches containing statues, blind arcading and pinnacled tops. They are connected by the parapet with a statue to the centre. The set-back gable above has a transomed six-light window. The transomed east window, largely concealed by the east-end chapels, comprises a central three-light window with a pointed arch and a lancet window to either side. The two chapels to the south-east corner have square ends, large corner buttresses with offsets, and parapets with two rows of quatrefoils. The windows are in the Perpendicular style, as opposed to the French Gothic style windows of the other chapels. The remaining east-end chapels have polygonal ends. The next chapel has a parapet with blind arcading with trefoil heads. The Lady Chapel has windows divided by buttresses with offsets and cusped gables; single-light windows with trefoil heads light the crypt beneath. To the north-east of the Lady Chapel is an octagonal stair turret and two further polygonal chapels with plain parapets.

The adjacent sacristy has a crenellated parapet with a four-light east window above a square projection, and a five-bay north elevation with three-light windows above lean-to projections. The bays are divided by buttresses with offsets.

The north transept is of two bays with buttresses with offsets, and lean-to bays to either side. Its north elevation includes a large wheel window above a band of blind trefoil-headed arcading. The north aisle has a plain parapet and dividing buttresses with offsets.

Throughout the interior is a moulded, rib-vaulted ceiling in the 13th-century French Gothic style, with stone infill. The unfinished eight-bay nave is in the Perpendicular style with a pointed-arch arcade, with the triforium and clerestory above, and north and south aisles. The clustered arcade piers are composed of four octagonal shafts with moulded bases and capitals. Between the arcade bays are angel corbels supporting clustered shafts with moulded capitals from which the ceiling ribs spring. The triforium gallery has paired, plate-tracery openings with ogee arches and quatrefoils, and above are three-light, traceried clerestory windows. The nave has a parquet floor with stone paving to the aisles. At the east end of the north aisle is the Chapel of St Lawrence, designed by Dunn and Hansom and refitted by Walters in 1898, with an altar with a Perpendicular screen behind and a relic cupboard painted by Nathaniel Westlake.

The crossing is defined by tall clustered shafts with foliate capitals that terminate above the triforium gallery; this continues around the sides of the north and south transepts. To the north transept the galleries are connected by a balustraded gallery with two rows of pierced quatrefoils supported on a Lombard-style frieze with corbels carved with figures. The north transept, originally functioning as the sanctuary and now the Chapel of St Oliver Plunkett, has an elaborately carved stone altar designed in 1882 by Dunn and Hansom and carved by Wall. On tall stone columns is a gilded oak reliquary of St Oliver Plunkett. The south transept is screened from the body of the church by a decorative stone wall with a central, pointed-arch doorway to the north cloister and flanking niches. Above is a Gothic, wood-carved organ screen of repeated vertical openings designed by Scott in 1931 and carved by Ferdinand Stuflesser.

The choir is in the Early English style with a square east end pierced with three tall, pointed-arch openings with statues beneath crocketed canopies to the dividing piers. The east window has stained glass designed by Comper. The pointed-arch north and south arcades have clustered piers with foliate capitals. Angel corbels between the arcade bays support the clustered shafts that rise through the tall clerestory bays (the triforium is not continued to the choir). The oak choir stalls, designed by Scott in 1931 to 1932 and based on the late-14th-century choir stalls at Chester Cathedral, are carved by Stuflesser. The front two rows of stalls, also carved by Stuflesser, were added in 1951.

The north choir aisle has three square chapels: Holy Angels, St Placid, and Seven Sorrows, all by Dunn and Hansom, each with stained-glass windows by Hardman and Company, and an early-20th-century parclose screen by F.C. Eden. The Chapel of the Holy Angels has a small Flemish triptych of about 1540. The Chapel of St Placid contains an altar and reredos of 1915 to 1916 with painted panels of six saints by Dame Catherine Weeks, coloured and gilded by Geoffrey Webb who also designed the archangels above. The Chapel of the Seven Sorrows has a reredos of 1892 by Dunn and Hansom and carved by Wall; it was recoloured and gilded by John Tolhurst in 1955. The central crucifixion panel is probably from Regensburg, Germany and dates from about 1480 to 1490. To the east is the Tudor-arched entrance to the sacristy. The Chapel of St Sebastian was designed by Garner and refitted by Comper in 1929 to include a reredos with an alabaster figure of St Sebastian and a Perpendicular stone screen; the west bay of the screen was completed by Gilbert Sullivan in 1972. To the east is a second Tudor-arched entrance to the sacristy with an oriel window above, and the Chapel of St Sylvia, designed by Walters. The polygonal chapels of St Joseph and St Vedast are to the north-east corner of the ambulatory and both have stained-glass windows by Hardman and Company.

The Lady Chapel by Dunn and Hansom projects to the east, in line with the choir. It has a polygonal east end and nine stained-glass traceried windows by Comper. The three in the apse were fitted in 1899 to 1911; the rest in 1919 to 1927. To the north and south walls are blind arcading with trefoil heads. The fixtures and fittings by Comper include an English-style altar with alabaster and gilt reredos; a gilded screen with four gilded relic chests and a central cross; a square tester of 1912 with the Coronation of the Virgin depicted on the underside; and Spanish-inspired wrought-iron entrance gates to either side of a painted and gilded limewood statue of the Virgin. To the south is the Chapel of the Sacred Heart which contains decorated ceramic reliefs of 1954 to 1956 by Adam Kossowski and three stained-glass windows by Comper. To the south-east corner are the Chapels of St Benedict and St Isidore, both with stained-glass windows by Lavers, Barraud and Westlake. The Chapel of St Benedict has a triptych reredos designed by Walters and painted by Westlake and a parclose screen also by Walters. The Chapel of St Isidore has a stone-carved reredos designed by Walters and a marble pavement designed by Garner and made by Farmer and Brindley. In the south choir aisle is the tomb to Cardinal Gasquet, designed by Scott as a recumbent effigy with his head held by an angel and at his feet the figure of History. It is sculpted of grey Palombino marble by Edward Carter Preston and covered by a carved, painted and gilded pine canopy.

The outer wall of the south choir aisle divides the abbey from the north cloister and includes a limewood sculpture of the Virgin and Child attributed to Nicolaus Gerhaert of Leiden of about 1470. A stone vaulted staircase designed by Garner leads to the gallery chapels above. These have rib-vaulted ceilings, parquet and tiled floors, and stone balustrading to their north wall.

The sacristy, accessed from the north choir aisle, has a three-room plan, parquet flooring and timber-panelled ceilings. The decoratively carved oak fixtures and fittings are designed by Walters, possibly executed by the De Wispelaere workshop in Bruges. They include an altar and triptych reredos at the east end, a bank of back-to-back vestment benches with drawers, each associated with a particular chapel, and pairs of fitted cupboards to the arcaded side walls. Between the bays are carved coats of arms and above a decorative cornice are the clerestory windows. There are also elaborately stone-carved piscinas, the one to the west end has a tap and carved canopy.

The north cloister has a rib-vaulted ceiling with banded-stone infill. The ribs and the piers beneath have carved ornament, and the piers have carved foliate capitals and moulded bases. The window bays are within recessed pointed arches, and the floor is laid with polychrome tiles laid in geometric patterns.