Two ways a foreign paper gets believed
There are two systems for showing that a signature on a foreign paper is real. One is the apostille: a single slip that every state inside a shared treaty honours without asking more of you. The other is the older chain, where the receiving state has an officer of its own look at the file before it counts for anything.
Where the destination stands on the Convention
Democratic Republic of the Congo has not joined the Hague Apostille Convention, so it works to that older chain. Britain joined long ago, which is why the slip is issued here at all, but a treaty only shortens a journey when both ends belong to it. A British paper bound for Congolese use therefore needs a consular stamp whatever else already sits on it.
The order the two stages follow
The British half comes first and it is impersonal. One office covers the whole country, it acts through the post, and no desk in London does this work. It will mark a register copy, a court copy, or a paper signed by someone whose signature it already holds, then return the file the way it came.
The second half is where an apostille from United Kingdom to Democratic Republic of the Congo parts company with a route into Europe. A consular officer reads the paper itself, logs it, and keeps a rhythm of their own. Because that desk stamps on top of the British mark, the two halves cannot swap places or run side by side.
What the order means for your calendar
Nobody publishes a fixed clock for a route with two desks in it, so treat the consular half as the stage that sets your date. A file tied to a contract start, a court hearing or a school term should leave London with weeks in hand rather than days, because each stage adds its own round of post.
Readers usually arrive asking what you need for an apostille for Democratic Republic of the Congo and leave with a consular checklist instead. The short answer is a copy that can be replaced, the British mark on top of that copy, and enough room booked in the diary for the officer who adds the final stamp.