What finished actually means
Being finished is not a property of the paper. It is the moment a named desk takes the file and asks for nothing further. When that desk sits abroad, nothing done in the United Kingdom can settle the question on its own, however official the result looks when it comes back to you.
Where Cameroon stands
Cameroon has not joined the Hague Apostille Convention. Papers meant for Cameroon require embassy legalisation instead, so the road runs past the British stage and closes at a consular desk. That one point moves the finish line out of the country, and it is why the British part of this road can never be the last part of it.
The office people stop at
The FCDO Legalisation Office at PO Box 6255, Milton Keynes MK10 1XX issues British apostilles for the whole country by post, with no counter anywhere to attend. Its published charge is £45 a document by standard post, or £40 a document next-day where the sender is a registered business. Both figures are real, and neither of them buys a finish here.
Reading your own file
So judge the file by what it still needs rather than by how decorated it has become. Work backwards from the last desk on the road and treat every British mark as an interim step. Anyone reading up on what you need for an apostille for Cameroon is really asking about the start of that road, not the end of it.