Two roads out of Britain
One road finishes with a single slip that Convention countries read on sight. The other keeps going until a foreign desk has added its own stamp. Eritrea is on the second road, so document legalisation for Eritrea describes the errand properly, while the word apostille describes only its opening move.
Where Eritrea stands
Eritrea has not joined the Hague Apostille Convention. An apostille issued in Derby for use in Eritrea is therefore not a finished document, and no amount of care at the British end turns it into one. An apostille from United Kingdom to Eritrea is best understood as stage one of two, useful and unavoidable, but not the last word.
The office that holds the record
Derby Register Office at Riverside Chambers, Full Street, Derby DE1 3AF is where a local birth, marriage or death entry actually lives. It can print a fresh certified copy of that entry on request, which is what makes it the natural first stop. What it cannot do is speak to anyone abroad or add a mark meant for a foreign reader.
Who charges you, and for what
The register office charges its own way for a reprint, and no figure for that belongs here. The Legalisation Office publishes £45 per document by standard post and £40 per document next-day for registered businesses. A third charge arrives at the consular stage. Three desks means three separate bills, which is why anyone asking what you need for an apostille for Eritrea should budget in parts.
The office that stamps, and the desk after it
The Legalisation Office is not where your record lives. It deals with the signature on the sheet in front of it and nothing more, which is why it never asks why you want the paper. The consular desk that follows makes a different judgement again, about its own country's rules. Nobody in the chain reviews the whole job, so that part stays with you.