The following text is from the original listed building designation:
KNOLE PARK 1. 1614 The Bird House TQ 55 SW/4/86 13.4.51 II 2. Ornamental "Gothic" summerhouse now converted into gamekeeper's cottage. Octagonal in shape with conical slate roof and 2 supporting towers at side with projecting gabled porch to North with statue in apex of gable. Small Gothic casement windows and dormers. Rough plastered elevations with flat dentilled eaves and gutter. This building is set in a grotto with C18 "ruins" nearby. The summerhouse is probably early C19, but incorporates an older structure. Listing NGR: TQ5436853978 (1)

Description from record TQ 55 SW 22 :
[TQ 5437 5397] Birdhouse [NAT] (2) The Bird House, Grade II, Knole Park. Ornamental "Gothic" summerhousenow converted to gamekeeper's cottage. Probably early 19th century, but incorporates an older structure. (For full description see list.)(3) In Knole Park (TQ 55 SW 17), a little way beyond the south east cornerof the walls, the Birdhouse, an octagonal folly built c. 1761. The doorway and two windows, set into a wall left of the Birdhouse, perhaps genuinely medieval and said to have come from Otford Palace (TQ 55 NW 18). (4)

<1> English Heritage, List of Buildings of Special Architectural or Historic Interest (Map). SKE16160.

<2> OS 1:2500 1966 (OS Card Reference). SKE48208.

<3> DOE(HHR) Dist of Sevenoaks UD Kent Sept 1972 34 (OS Card Reference). SKE41044.

<4> The Bldgs of Eng W Kent and the Weald 1980 363 (J Newman) (OS Card Reference). SKE50144.