Large country house. Mid C12, mid C13, early C17, some rebuilding by Robert Smythson now largely remodelled. John Smythson c.1623 built the riding school and stables. The latter demolished in C18, the former now the much remodelled chapel and library. Mid C18 Gothic alterations carried out possibly by John James or Thomas Carter. Mid C18 garden improvements by Francis Richards. 1775-7, east front remodelled by Cart, subsequently largely remodelled. 1790-2 Repton carried out improvements, moving earth to the west front of the building and turning the ground floor into a basement. 1860-79 programme of building for the 5th Duke, including underground rooms and tunnels. Early 1890s, the riding school converted to library and chapel, in the main to designs by Henry Wilson. 1900-02 work carried out by Ernest George of George and Yates. Notably the remodelling of the Gothic Hall, additions to the east front and the fire damaged west front. Ashlar with some render. Moulded copper tile roofs. Many ashlar stacks. L-plan extending via a curved picture gallery wing to a further rectangular chapel and library wing, former riding school extension. 14 bay, 2 storey plus attic, over basement. Central pedimented slightly projecting 3 bay centre, and single bay 3 storey pavilions topped by parapets at either end. 2 storey ranges have modillion cornice. Central doorway has ornate Baroque-style porte-cochere with bold rustication by George. All windows glazing bar sashes, except the 5 bays to right of central section, which have wooden mullions and leaded casements. 2 storey, 13 bay, north front at right angles, has glazing bar sashes throughout with some blind openings and is topped with a balustrade. Single 3 storey tower projects, 3rd bay from the west. Domed lantern over 7th bay from west. South front, 17 bays, 3 storeys. Central, slightly projecting bay has rusticated pilaster strips and is topped with a segmental pediment, then 2 outer bays, and single slightly projecting, 4 storey towers, beyond projecting 2 bay, 3 storey, pavilions with pediments, rusticated pilasters and 3 bays beyond, all surmounted by balustrade. Glazing bar sashes to most windows. Doorway 1743 plaque and 1902 reconstruction plaque. East front has main 2 storey plus attic and basement 14 bay front, with off centre 3 bay, slightly projecting, 3 storey pedimented central pavilion with 3 semi-circular rusticated openings in ground floor, to heft, 6 bays, and to right, 5 bays all topped with parapet. Baroque-style rusticated Venetian doorway 2nd bay from north. Beyond to left, 4 bay, 3 storey pavilion, topped with balustrade, with projecting columned entrance loggia over rusticated base with barrel vaulted roof. Glazing bar windows throughout. North front, very irregular with single storey extension, topped by Gothic gable with pinnacles. From here projects 2 storey, rendered and ashlar picture gallery wing, with small 3 light wooden casements, linking main house to former riding school block. At either end gabled wings with ornate art nouveau decorative work. This block 2 storey, 15 bays, with parapet and coped gables with kneelers topped with pair of ornate clock cupolas. Glazing bar sashes throughout. To the rear, each side, are single coped walls with single recessed, arches and keystones on each side, terminating in vermiculated rusticated and decorated piers, each topped with 4 orbs supporting an obelisk. To the south are many glazed skylights to sunken ballroom. Interior. Mid C13 vaulting and doorway in basement. Robert Smythson fireplace decorated with strap work, ornamental urns and brackets with Delft tiles. Bursars study with sexpartite stone rib-vault with Cavendish and Ogle crests, pendant boss and stone tablet with Cavendish stag, panelling as at Bolsover. Set of C18 state rooms mostly remodelled in C19. The Great Hall retains C18 pendant plaster vault. Mannerist revival archway dated 1749, small Gothic room dated 1749 with decorative plasterwork. Library with bookshelves and inglenook alabaster fireplace by Pomeroy with decorative plaster work over and wooden panel surround. Extraordinarily elaborate and sumptuous marble colonnaded arts and crafts chapel with exceedingly fine fittings. Including bronze lectern, decoratively carved benches, Sheffield plate altar front, C17 altar piece by Honthorst, marble, brass and enamel font, marble pulpit. Elaborate bronze entrance doors 1909 by P. Wilson. Decorative barrel vaulted roof. (NCC/js)