Historically, the term has most commonly been used to refer to Black people of New Commonwealth origin, of both West African and South Asian descent. For example, Southall Black Sisters was established in 1979 "to meet the needs of black (Asian and Afro-Caribbean) women". Note that "Asian" in the British context usually refers to people of South Asian ancestry.
"Black" was used in this inclusive political sense to mean "non-white British".
In the 1970s, a time of rising activism against racial discrimination, the main communities so described were from the British West Indies and the Indian subcontinent. Solidarity against racism and discrimination sometimes extended the term at that time to the as well.
Several organisations continue to use the term inclusively, such as the Black Arts Alliance, who extend their use of the term to Latin Americans and all refugees, and the National Black Police Association. The official UK Census has separate self-designation entries for respondents to identify as "Asian British", "Black British" and "Other ethnic group". Due to the Indian diaspora and in particular Idi Amin's expulsion of Asians from Uganda in 1972, many British Asians are from families that had previously lived for several generations in the British West Indies or Southeast Africa.
The 1991 UK census was the first to include a question on ethnicity. As of the 2011 UK Census, the Office for National Statistics (ONS) and the Northern Ireland Statistics and Research Agency (NISRA) allow people in England and Wales and Northern Ireland who self-identify as "Black" to select "Black African", "Black Caribbean" or "Any other Black/African/Caribbean background" tick boxes. For the 2011 Scottish census, the General Register Office for Scotland (GOS) also established new, separate "African, African Scottish or African British" and "Caribbean, Caribbean Scottish or Caribbean British" tick boxes for individuals in Scotland from Africa and the Caribbean, respectively, who do not identify as "Black, Black Scottish or Black British". In all of the UK censuses, persons with multiple familial ancestries can write in their respective ethnicities under a "Mixed or multiple ethnic groups" option, which includes additional "White and Black Caribbean" or "White and Black African" tick boxes in England, Wales, and Northern Ireland.
Black British was also a term for those Black and mixed-race people in Sierra Leone (known as the Krio) who were descendants of migrants from England and Canada and identified as British. They are generally the descendants of black people who lived in England in the 18th century and freed Black American slaves who fought for the Crown in the American Revolutionary War (see also Black Loyalists). In 1787, hundreds of London's black poor (a category that included the East Indian seamen known as lascars) agreed to go to this West African colony on the condition that they would retain the status of British subjects, live in freedom under the protection of the British Crown, and be defended by the Royal Navy. Making this fresh start with them were some white people (see also Committee for the Relief of the Black Poor), including lovers, wives, and widows of the black men. In addition, nearly 1200 Black Loyalists, former American slaves who had been freed and resettled in Nova Scotia, also chose to join the new colony.