The treaty route and the consular route
There are two ways to satisfy a foreign office that a British signature is real. The treaty route uses one slip and no further argument. The consular route asks the receiving state to look at the file through its own officer. Cameroon uses the second, so the British stamp is the opening move rather than the closing one.
Cameroon's standing under the Hague Convention
Cameroon has not joined the Hague Apostille Convention. A British paper heading to Douala, Yaoundé or Buea requires embassy legalisation regardless of what the Legalisation Office has already applied. Britain signed the treaty long ago, and that is why the stamp is available in the first place, but a shortcut needs both ends inside the agreement.
What actually happens in Sheffield
The local part of this job is collecting paper, not queuing. The Legalisation Office keeps no counter in Sheffield and works entirely by post, so the city's role is supplying the source: the Register Office at the Town Hall for civil entries, a university for a degree, a solicitor or company officer for a business record.
An apostille from United Kingdom to Cameroon then runs on two clocks. The British one is steady and priced up front. The consular one belongs to another state and moves at its own speed, so a start date at a school or hospital should be treated as a deadline with weeks of margin, not days.
Two languages, and the jobs behind the paperwork
Cameroon is unusual on this route because it runs public business in French and in English. That single fact changes how you prepare a file. An English document may be read as it stands in an English-speaking region, while the same paper going to a French-speaking office is easier to process with a French version bound in after the stamps are applied.
The work behind these files is mostly teaching, medicine and the energy sector. A degree, a transcript and a police record commonly move as a set, followed by an employer letter. Company records appear where a Sheffield firm registers locally. Family records travel less often, and those are the ones to replace with a certified copy before anything leaves.