The paper with nothing behind it
Most documents that get marked in Britain come from a register. Someone can print another one, sign it again, and hand it over the same week. An academic award works differently: it was issued once, to you, and the sheet in your drawer is the object everybody means when they talk about your qualification. That single difference shapes the whole errand.
It shows up first as a question of care. There is no cheap second copy waiting in a filing cabinet in Cathays Park, so the certificate travels as itself and the sensible habits follow — a scan kept at home, a tracked envelope, and no more journeys for the sheet than the job actually needs.
Whose signature the office is standing behind
The marking office fastens its certificate to a signature. On a register copy that signature belongs to a registrar and is recognised at once. On an academic award it belongs to the school, college or university that granted it, and the position varies with the body: some signatures are already known to the marking office, and others reach it by a longer path.
Whether a notary has to see the sheet before any of that is not settled by a general rule, and it would be wrong to claim otherwise. It depends on the issuing body and on what the receiving country asks for. The honest description of how to apostille a Diploma is that the first step varies while the second never does.
Priced per sheet, which academic files feel
The standard postal service costs £45 per document; a next-day service at £40 per document is open to registered businesses. Electronic apostilles are issued in Britain as well. Everything runs through one central office and moves by post, so the wait is that office's own time plus the envelope in each direction, with nothing to book and nobody to see.
Academic files feel the per-sheet charge more than most. A degree certificate, a transcript of marks and a letter of award are three documents and three charges, not one job. Deciding which of the three the foreign body actually named is the difference between a modest bill to apostille a Diploma in the United Kingdom and one three times the size.
What the mark covers, and what it does not
It covers provenance and nothing else. The mark does not say your course was three years long, that the grade converts to any foreign scale, or that a ministry abroad recognises the award. It does not put the certificate into another language either, so where the receiving country works in its own, that translation is arranged separately once the mark is on the sheet.
This is the point where academic paperwork most often goes wrong. A marked certificate arrives abroad and is treated as a claim about the quality of the qualification, when all it establishes is that the signature is real. The recognition question is answered by the receiving body's own rules, on its own timetable, and no British stamp reaches into it.