Richard Betham, described by Robertson as "a gentleman, whose erudition was truly respectable; and to whose politeness and friendship I am highly indebted" was well connected, counting as friends such as David Hume, Adam Smith and Joseph Black. He lived at the Hague in Onchan later occupied by the Bullocks. He had been appointed receiver general and water bailiff following the 1765 Act of Revestment - the only post for which London did not keep on the pre-revestment appointees by the Duke of Atholl. It would appear however that the post was effectively a sinecure as the appointee after Betham's death in 1789 (31 May) set foot just once on the Island.
Genealogical details re Richard Betham seem difficult to find - the family name Betham appears most common in the Westmoreland region ...
Betham's wife, Mary, was the sister of Duncan Campbell (1726-1803) - a wealthy ship owner in the West Indian trade, from reported research in the PRO his ships were not in the slave trade though he was not in favour of of protests against this trade as they would hurt his sugar importation; he was also a provider of the various prison hulks used to house convicts on their way to transportation in Australia. Mary died in 1766, aged 42, and is buried in Onchan. A Margaret Betham is also noted as being buried in Onchan in 1783 - possibly his sister come over to keep house as he had two young daughters Elizabeth and Anne.
"Scotland Marriages, 1561-1910," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:XTY1-QL2 : 10 February 2018), Richd. Bitham and Mary Campbell, 11 Sep 1748; citing Glasgow,Lanark,Scotland, index based upon data collected by the Genealogical Society of Utah, Salt Lake City; FHL microfilm 102,924, 919,484.
Betham-8 was created by Clare Brodie through the import of Brodie (cbrodie194) (1).ged on Jul 27, 2014. See the Changes page for the details of edits by Sarah Mason, Emma (McBeth) MacBeath, Heather Stevens and others.