19,19a and 20, Broad Sanctuary SW1

Nos. 19, 19A, and 20 Broad Sanctuary are school houses that form part of a range of Abbey buildings originating from the late 14th and 15th centuries. They incorporate sections of the Cellarer's Building, the Abbey Guest House, and remnants of the Blackstole Tower. These structures were taken over and extended by the school in the 15th and 16th centuries, with alterations and additions made in the 17th and 18th centuries. The buildings are constructed of stone rubble with 18th-century brickwork on the second floor, featuring leaded and tiled roofs and three storeys of irregular height.

Number 19 has a six-window range, including the Blackstole Tower, while Number 20 has an irregularly fenestrated four-window range. The archway beneath the Blackstole Tower on the left is from the late 14th century, featuring carved spandrels and a tierceron-vaulted passage that leads to Number 19A. Number 20 has a later 18th-century Gothick doorway to the right of the Blackstole Tower, complete with a fanlight, sidelights, and a drip mould-cornice above. Number 19 features recessed glazing bar sashes in stucco reveals and a two-light stone mullioned window above the doorway on the third floor. Number 20 has small Gothic lights grouped irregularly on the ground floor, with glazing bar sashes and a three-light stone mullioned window with cusped heads on the upper floors. The brick parapet is partly crenellated.

At the rear, there are late 17th and 18th-century brick additions, including two three-storey fronts that connect to the Little Dean's elevation of the tower and archway of Number 18. One of these fronts has a Venetian window on the first floor, while the other has a three-bay front with recessed sashes under flat gauged arches, both featuring pedimented doorways. Inside Number 20, remnants of the Cellarer's Building and Abbey Guest House can be found, including a tierceron-vaulted ground floor with wall shafts and some original windows remaining in the east wall. On the first floor, a late 14th-century flat pitched roof with partially surviving tie beams is present.