Gun captured at Lagos, Bight of Benin, Africa, Quadrangle Portsmouth Dockyard, photographer unknown, State Library of New South Wales.
On far right - Admiral Sir Henry William Bruce, Commodore of the West Africa Squadron who negotiated and signed the Treaty between Great Britain and Lagos of 1 January 1852.
From Wikipedia - In 1849, Britain appointed John Beecroft Consul of the Bights of Benin and Biafra, a position he held (along with his governorship of Fernando Po) until his death in 1854. At the time of Beecroft's appointment, the Kingdom of Lagos (under Oba Kosoko) was in the western part of the Consulate of the Bights of Benin and Biafra and was a key slave trading port. In 1851 and with pressure from liberated slaves who now wielded political and business influence, Britain intervened in Lagos in what is now known as the Bombardment of Lagos or Capture of Lagos resulting in the installation of Oba Akitoye and the ouster of Oba Kosoko. Oba Akitoye then signed the Treaty between Great Britain and Lagos abolishing slavery. The signing of the 1852 treaty ushered in the Consular Period in Lagos' history wherein Britain provided military protection for Lagos.
en.wikipedia.org/wiki/Lagos 