The following text is from the original listed building designation:
TQ 66 NE COBHAM 5/37 27.8.52 The Mausoleum, Cobham Hall (formerly listed as Mausoleum in Park)
I
1783 designed by James Wyatt for the 4th Earl of Darnley. Never used. Portland stone. Square with projecting chamfered corners. Surmounted by a pyramid. Roman Doric order, fluted columns in antis on face, prostyle on angles. Lunette openings above cornice. Tomb chests above the angle architraves. Circular chapel up several steps with red marble Corinthian order and coffered dome of plaster. Basement at lower level held 32 coffin shelves under shallow stone dome.
Condition poor, disrupted by vegetation and battered by vandals. The iron railings round the south area have been removed.
Listing NGR: TQ6797468916
(1)

Description from record TQ 66 NE 28 :
(TQ 69436838 - sited from HHR Map) TQ 66 NE COBHAM 5/37 27.8.52 The Mausoleum, Cobham Hall, (formerly listed as Mausoleum in Park) I 1783 designed by James Wyatt for the 4th Earl of Darnley. Never used. Portland stone. Square with projecting chamfered corners. Surmounted by a pyramid. Roman Doric order, fluted columns in antis on face, prostyle on angels. Lunette openings above cornice. Tomb chests above the angle architraves. Circular chapel up several steps with red marble Corinthian order and coffered dome of plaster. Basement at lower level held 32 coffin shelves under shallow stone dome. Condition poor, disrupted by vegetation and battered by vandals. The iron railings round the south area have been removed. (2)

In 2001-2002 Archaeology South-East carried out clearance works within the mausoleum and the surrounding dry moat. The upper floor of the mausoleum collapsed after a major fire in 1980. Successive bonfires were then held within the ruin causing further collapse in the mid to late 1980s. The structure had evidently been robbed of key architectural elements prior to this event. (3)

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

<2> DOE(HHR) Dist. of Gravesham, Kent. July 1983 3 (OS Card Reference). SKE41122.

<3> Archaeology South-East, 2002, Archaeological Works at Darnley Mausoleum, Cobham Park, Cobham, Kent (Unpublished document). SKE17817.