Sarah Long 29/7/2021: There is no evidence that I can find that James was the son of the parents he is attached to. The baptism registers for Combe and the Bishop's transcripts of those registers between 1791 and 1800 no longer exist. There were a number of Harris couples having children baptised in Combe before and after those dates (William and Mary, Joseph and Jane, James and Sarah, William and Esther) so he could have been the son of any of those couples. There are no baptisms in the surviving Combe registers of children of Robert and Elizabeth. Until there is a verifiable source confirming that he was the son of Robert and Elizabeth this relationship is unproven.
"England and Wales Census, 1851," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:SGXS-DWW : 24 October 2017), James Harris, Coombe, Oxfordshire, England; citing Coombe, Oxfordshire, England, p. 14, from "1851 England, Scotland and Wales census," database and images, findmypast (http://www.findmypast.com : n.d.); citing PRO HO 107, The National Archives of the UK, Kew, Surrey.