The route Mauritania uses
State the rule first so the rest reads clearly. Mauritania has not joined the Hague Apostille Convention, so document legalisation for Mauritania goes through the consular chain: a British stage, then a stamp from Mauritania's mission in the United Kingdom. An apostille for Mauritania on its own leaves the paper short of what the far end expects. The good news is that the earlier half of the work is the same either way, so nothing you do at the start is wasted.
Place of issue, not place of residence
People assume the route follows the person, and it follows the paper instead. A family in Sunderland can easily hold records from three countries: a marriage certificate registered here, a birth record from somewhere else, a qualification awarded overseas. Living at one address does not put them all in the same queue. Each sheet belongs to whichever country's offices can vouch for the hand that signed it, and that is settled on the day it was issued.
This matters because the middle stage is a signature check. An apostille from United Kingdom to Mauritania rests on a British office recognising a British signature it already holds on record. Present a sheet signed abroad and there is nothing for it to compare. Nobody is being awkward; the office simply has no way to say anything true about a hand it has never seen. Sorting your pile on that basis takes ten minutes and prevents a wasted fee.
How a British paper travels
For a British civil record the path is short and local at first. Sunderland Registration Service issues certified copies of births, marriages and deaths, so a fresh copy can be ordered and the certificate you keep at home never has to move. The FCDO Legalisation Office then attaches its certificate to that copy and returns it by post; it holds no public counter anywhere. The consular stamp for Mauritania is the last mark, and it goes on top of the British one.
What the Mauritanian stage looks for
At the far end the questions narrow again. A mission wants the British stage plainly complete, the paper whole and unaltered, and a request that names the person the record concerns. So an apostille issued in Sunderland for use in Mauritania is a stage rather than a finished article, and the bundle you hand over should show its full history on its face. A mixed pile of British and foreign papers arriving together is where most delay at this desk comes from.
Cost and timing on the British half
The British stage is the priced part you can plan exactly. It costs £45 per document by standard post, with a next-day tier at £40 per document for registered businesses. Because the charge is per document, sorting out early which sheets can actually take this route also protects the budget. What follows at the consular desk carries its own charge, and the post between the two adds days that no fee shortens.