If you are asked to produce a document outside of the country issuing the document you need an Apostille. The Apostille takes the form of a seal on a separate sheet of paper attached at the end of the translated document or on the verso of the last translated page and is dated, numbered and registered by a Tribunal Official via the sworn translator.
It authenticates both the signatures of the Italian Law Court official who has signed the document and the sworn translator’s, making the document valid as if issued in any one member states signatory to the Hague Convention of October 5, 1961, though many of the countries that are not members recognise the authentication of the Apostille, too.
If your country is NOT in the list, then your translation has to go through a similar process called legalisation. All our translations can be sworn and legalised with or without Apostille at any Law Court in Italy.
This website clearly explains what to do to have a document ‘legalised’ (or apostilled) in the U.K.