Wikipedia
An Agent-General is the representative in the United Kingdom of the government of a Canadian Province or an Australian State and, historically, also of a British colony in Jamaica, Nigeria, Canada, South Africa, Australia or New Zealand and subsequently, of a Nigerian Region. Australia and Canada's federal governments were represented by High Commissions, as are all Commonwealth national governments today.
Starting in 1886 Quebec and the federal Canadian government also appointed agents general to Paris. The first, Hector Fabre, was dispatched by the province of Quebec but was asked by the federal government to represent all of Canada. He and his successor, Philippe Roy, continued to represent both Quebec City and Ottawa in France until 1912 when the federal government asked Roy to resign his Quebec position to avoid conflicts of interest. Canadian provinces have also appoint agent-generals (called delegate-generals in Quebec beginning in the 1970s) to other countries and major cities.
Following a military coup in Nigeria in 1966, the federal system was abolished, and the posts of the Agent-General of Nigerian Regions in London were subsumed in the Nigerian High Commission.
By the 1990s, some Australian state governments regarded the office of their Agent-General in London as a costly anachronism, even for promoting tourism and investment, and have since been closed and subsumed into the Australian High Commission, see List of High Commissioners of Australia to the United Kingdom. The majority of Australian States continue to have Agents General in London, but operate from Australia House rather than maintain separate premises.
Many Canadian provinces similarly are no longer represented by an Agent-General, although Quebec continues to have a Government Office (Délégation Générale du Québec à Londres) in London and several other cities around the world and Ontario has a representative who works out of the Canadian Embassy in Washington, DC.