This entails the affixing of a seal called an Apostille by the Foreign and Commonwealth Office to the notarised document under the Hague Convention. The effect is to confirm to the receiving jurisdiction that I am a Notary.
Not all documents require legalisation, most Commonwealth countries for example do not require an Apostille.
The Legalisation Office has moved from London to Milton Keynes. I use an agent at modest cost to obtain an Apostille as this cuts the time down to 4 to 5 days.
The Foreign and Commonwealth Office charges are at present £28.
If a document is required urgently, it is still possible to obtain legalisation in London but at a cost of £67.