One stamp is not the end of the story here
A great many applicants type in apostille for Sri Lanka expecting a single stamp to close the whole matter completely, the way it does for a Hague member country, but that is not quite how the route works for this particular destination in practice today.
Sri Lanka asks for a further check from its own mission in the UK once the Legalisation Office has finished its part, so the UK stamp is best understood as the opening move rather than the entire game on its own.
This is not unusual among countries a Stoke-on-Trent applicant might send papers to; some accept the single stamp outright, others still run a longer chain of their own entirely, and Sri Lanka currently sits firmly and clearly in that second group.
The two offices a Stoke-on-Trent paper passes through
A civil record such as a birth or marriage certificate can start life as a fresh certified copy from Stoke-on-Trent Register Office, Civic Centre, Glebe Street, so the true original never has to leave your hands at any point in this whole two-part process.
That paper, or any other signed document sent forward as it already stands, goes next to the Legalisation Office (Foreign, Commonwealth & Development Office) at PO Box 6255, Milton Keynes MK10 1XX for its signature check and its own stamp before anything else can happen.
An apostille issued in Stoke-on-Trent for use in Sri Lanka does not finish there, though; a second, separate look from the Sri Lankan mission in London still stands between that stamp and the paper being properly ready for its long trip abroad.
Only when both checks are behind it does the paper genuinely count as finished and ready. From that point it can be sent on to Sri Lanka and handed over there for whatever purpose first prompted the whole exercise back at the beginning.
A photocopy kept safely before anything is posted costs nothing at all and is worth having regardless, since a question can come up at either stage about exactly what was originally sent through this longer, two-part route to Sri Lanka.
What the UK office charges, and what it does not
The Legalisation Office charges £45 per document by standard post, or £40 per document for a registered business choosing the faster next working day service instead, an option that stays closed to a private individual applying entirely alone for a single certificate.
Standard post for that UK part takes up to 25 working days, folding in the office's own checks rather than only the days spent travelling through the postal system on each separate leg of the whole journey there and back again.
None of that fee or that timescale reaches into the second check. An apostille from United Kingdom to Sri Lanka still needs the mission's own legalisation afterwards, and that mission fixes its own fee and its own pace entirely independently of the UK side.
Typical reasons people need this for Sri Lanka
Document legalisation for Sri Lanka is the accurate name for the whole two-part route described here, and people follow it for a Sri Lankan property matter, an inheritance case, a marriage recognised there, or paperwork behind a family visa application of some kind entirely.
What you need for an apostille for Sri Lanka is, in the end, patience across two separate offices rather than confidence in a single stamp: the UK side is fixed, predictable and published, while the mission's own half sets its own entirely separate terms.
Keeping a scanned copy of anything posted costs nothing at all and can be genuinely useful later on, since either office along this longer route may raise a question about exactly what was originally sent for legalisation to Sri Lanka in the first place.