The following heading for the earlier name is a valid AACR 2 heading: Historical Society (Great Britain)

Info. from LC: (Camden Society incorp. with the Royal Historical Society, 1897)

Information from 678 converted Dec. 19, 2014 (Founded 1868 as the Historical Society; name changed to present form 1872)

Wikipedia, June 10, 2019 (The Royal Historical Society is a learned society of the United Kingdom which advances scholarly studies of history. The society was founded and received its royal charter in 1868. Until 1872 it was known as the Historical Society [no publications found in OCLC]. In 1897, it merged with (or absorbed) the Camden Society, founded in 1838. It is now based at University College London)