This is the mansion at Bletchley Park. Also known as Bletchley Park Mansion.

It is Grade II listed.

Large house, now offices. 1860 altered and extended 1883-6 and c1906 for HS Leon. Red brick in Flemish bond with ashlar dressings; principal gables half-timbered with pebble-dashed infill, some others tile-hung; Welsh slate roof with red tile ridge; brick stacks, with clustered flues, ribs and bands. Transomed wooden windows, principal windows with leaded upper lights. Decorative wooden barge boards and finials to gables. Large rambling house, of 2 storeys with partial attic. Entrance elevation: 6 bays. Lavish ashlar detailing including architraves. Entrance in bay 2 has internal, vaulted, porch protecting panelled half-glazed double-door with side lights, traceried upper part and fanlight the latter leaded and with coloured glass. Flanking porch are hexagonal brick columns surmounted by panelled stone tops which flank base of 4-light oriel window with decorative base. Projecting from porch, and attached to it are 2 seated griffins on bracketed plinths. Shaped pediment with elaborate finial. Gabled bay 1 has projecting 2-storey canted bay with pretted eaves band and cornice below swept, domed, metal roof. On its left is single-storey wooden conservatory with traceried bays, formerly an open-sided loggia. Paired, gabled, bays 2 and 3 have ashlar framed triple window to ground floor with gableted butresses,and two canted bay windows over. Across bay 4 is 3 bay embattled ashlar loggia fronting elaborate - panelled double-door with canted bay window to right; inserted 1st floor window. Bay 6 has polygonal 2-storey bay window with shaped pediments screening finialed polygonal roof. Right return: 3 left-hand bays in same style as front, the rest plainer; but attached to right end is dovecote-like structure: octagonal, of 2 stages, having plinth; inserted ground-floor windows; ashlar upper stage with 2-light windows below string; and plain tile roof with gablets and finial. Rear: plainer having tradesmen's entrance; complex roofline, one roof having louvre with finialed lead cupola; and embattled tower with blue-brick decorative work and date (former steep hipped roof removed). Left return: in style of front, with ashlar canted and curved bay windows; paired, gabled, bays 2 and 3 decorative half-timbered 1st floor; shaped pediment to bay 4; and former loggia (much altered) across right-hand bays. Interior: high quality, elaborate, interiors survive, with panelling, panelled doors, decorative fireplaces, and decorative plaster ceilings. Entrance vestibule: stone columns and vaults. Entrance Hall: arcaded polished-stone screen wall and panelled area beyond with elaborate 2-stage, columned, ashlar fireplace surround and traceried panelling and painted glass to roof. Room at right end: Jacobethan fireplace; coffered ceiling with floral- decorated plaster panels. Stairhall: panelled; ground-floor arcade and deep floral frieze; decorative coved, coffered, ceiling over stair; fretted balustrade with carved surround and carved octagonal newels to stair panelled stair well. Library : elaborate wooden jacobethan inglenook with overmirror; fitted book cases and shelves; fluted frieze; compartmental ceiling with decorative plaster panels. Ballroom : linenfold panelling; wall recess flanked by clustered wooden columns from which spring traceried arches; elaborate plaster work to frieze and to coved, ribbed, ceiling which has pendant finials. Billiard room: brattished panelling and cornice; columns support ceiling ribs; wooden trusses. Additional fireplaces, panelling, and decorative doors, plasterwork and cornices to 1st floor.

Bletchley Park House was the headquarters building of World War II operational centre, in the grounds of which was the hut in which the vital cracking of the Nazis' Enigma Code occurred. Churchill was one of the important visitors to the house.