Does anyone know where the South Drawing Room is in Buckingham Palace?
I had thought it was the south west ground floor room :
https://c8.alamy.com/comp/G5RYDM/funeral-operations-centre-G5RYDM.jpg
but on closer inspection it definitely has a different fireplace to the room used for the interview.
On this ground floor plan the room above is called the dining room. It's possible that the room used for the interview is the one called the library between the dining room & the Council Room (now called the Bow Room).
https://i.pinimg.com/originals/6c/67/b8/6c67b8ed5ae6aac4d2097097b6abe0e8.jpg
The only other logical location for a "south" drawing room would be in the Blore wing on one of the three principal floors overlooking Buckingham Palace Rd.