This person is the subject of ongoing research. We have started by researching their relationship to the enslavement of people.
David Barclay was only a distant relative of the Barclay bankers. Barclay Brothers and Company failed in 1847 with heavy exposure in Mauritius, apparently taken on after Emancipation.
History of Parliament states that ‘He presented a Penryn anti-slavery petition, 30 May 1828’. (Howard Spencer, ‘BARCLAY, David (1784-1861), of Gloucester Place, Portman Square, Mdx.’, in History of Parliament Trust (ed.), The History of Parliament: British Political, Social & Local History [online], London, 1964 -, 1820-1832, <https://www.historyofparliamentonline.org/volume/1820-1832/member/barclay-david-1784-1861#constituency> accessed 16 June 2021.)
National Gallery painting connections
Donor: presented in 1853: NG235.
H. Spencer, 'BARCLAY, David (1784-1861), of Gloucester Place, Portman Square, Mdx', in History of Parliament Trust (ed.), The History of Parliament: British Political, Social & Local History, London 1964-, 1820-1832, https://www.historyofparliamentonline.org/volume/1820-1832/member/barclay-david-1784-1861
Checked and found — Item on publisher's website