The older method, still in use
Before the treaty existed, every country checked foreign paper through its own consular officer, and that method never went away. It still governs any route where the two states have not agreed to trust each other's stamps. Lebanon is such a case, so the British mark prepares the file and the consular mark completes it.
Lebanon and the Hague Convention
Lebanon has not joined the Hague Apostille Convention. A British paper heading for Beirut, Tripoli or Sidon requires embassy legalisation as a separate stage, whatever the Legalisation Office has already added. Britain signed the treaty long ago, which explains why the stamp is available here, but the shortcut only runs between two members.
What is prepared in Sheffield
The British stage is postal and centralised, so there is no counter in Sheffield to attend. The local work is assembling source papers: the Register Office at the Town Hall for birth, marriage and death entries, a solicitor for a power of attorney, a court for an order, and an awarding body for anything academic.
An apostille from United Kingdom to Lebanon often forms part of a longer legal matter rather than a single errand. Estate and property cases call for several documents at different stages, so it pays to order spare certified copies at the outset and keep them ready rather than repeating the whole journey each time.
Arabic, and the weight of property files
Arabic is the official language of Lebanese administration, so a stamped English document usually arrives with an Arabic version bound in. Have that prepared after the final mark. A translation made beforehand describes only the original sheet, and a notary or land office in Beirut is reading the completed bundle as a single object.
Property, inheritance and nationality questions give this corridor its character. A land matter can turn on a death entry issued in Sheffield decades ago, and a nationality claim on a birth entry of similar age. Because those cases move slowly and reopen often, spare certified copies are worth more here than on a work-driven route.