Apostille or consular route for Sierra Leone
An apostille is one certificate that Convention countries agree to take from each other with no further steps. Sierra Leone has not joined the Hague Apostille Convention, so that shortcut does not open. Papers headed there need document legalisation for Sierra Leone instead: the UK certificate first, then a stamp from the country's own consular desk. Both marks must be on the file when it lands.
A finished file points at one country
This is the part people plan around badly. The closing stamp is not a general seal of quality. It is applied by Sierra Leone's own mission, on Sierra Leone's authority, for reading inside Sierra Leone, and nothing in it speaks to any other government. An apostille issued in Newcastle upon Tyne for use in Sierra Leone therefore cannot be aimed somewhere else after the fact.
The effect is easy to plan for once you see it. If the same degree or birth record is wanted by two governments, you build two files, and each one walks the full route on its own. Deciding the destination early is cheaper than deciding it well later. Order the second certified copy from Newcastle Register Office while you are ordering the first one.
The Newcastle upon Tyne route, step by step
Start with the paper itself. Newcastle Register Office, at Civic Centre, Barras Bridge, Newcastle upon Tyne NE1 8QH, issues fresh certified copies of birth, marriage and death records, so the certificate in your drawer never has to travel at all. A court paper or a company paper starts instead with the body whose signature is at the foot of it.
The copy then goes to the FCDO Legalisation Office, PO Box 6255, Milton Keynes MK10 1XX. One central office covers the whole country and it works by post. It matches the signature against the specimen it holds and attaches its certificate to that sheet. What you need for an apostille for Sierra Leone starts with that check, though the file is not closed at that point.
Cost and timing on this route
The UK stage carries a set charge: £45 per document by standard post, or £40 per document on the next-day service that is open to registered businesses. The closing half is priced by the mission and is not fixed here. Because an apostille from the United Kingdom to Sierra Leone is only the first mark, plan for two charges rather than one, plus tracked postage each way.