Two roads, and the closed one
Two kinds of mark travel with British paper. One is the apostille, a single slip that Convention countries agree to read on sight. The other is consular legalisation, a chain of marks that ends at a foreign desk. Afghanistan works with the second kind, so an apostille from United Kingdom to Afghanistan is not the road, however often that word turns up in the email you were sent.
Where Afghanistan stands
Afghanistan has not joined the Hague Apostille Convention. That one point settles the shape of the whole errand. No apostille issued in Derby for use in Afghanistan will be taken on its own, and piling on extra paper does not change it. What applies instead is document legalisation for Afghanistan, built one stamp at a time and finished abroad.
The Derby end of the job
Derby Register Office at Riverside Chambers, Full Street, Derby DE1 3AF keeps the entries behind local birth, marriage and death records and can print a fresh certified copy on request. That copy is the sheet to put into the chain. The FCDO Legalisation Office, PO Box 6255, Milton Keynes MK10 1XX, then adds the British mark by post, and nothing in that stage happens in the city itself.
One published price, one open one
The British half has a figure you can write down: £45 per document by standard post, or £40 per document next-day for registered businesses. The charge follows the sheet, not the envelope, so the count of papers is the count of charges. The consular half has no published figure here, though an official charge does apply, so a sensible budget is one firm number plus room to move.
The file you keep at home
Readers looking up what you need for an apostille for Afghanistan reach the same answer twice over: not that certificate, and not one office alone. Because the job crosses two desks with a wait between them, the only continuous record of it is yours. Scans, dates and postal receipts kept from day one turn that gap from a blind spot into a normal pause.