In Italy when you apply for Citenzenship or for some other reasons, they will ask for apostilled documents. Getting this done for UK documents is actually simple. The UK Government has a service that will do it for you. Yes there is a fee, but it’s a sight lot cheaper than many other countries services.
You will often need marriage, birth certificated and especially your criminal records check legalised in many situations.
Get your document legalised – GOV.UK (www.gov.uk)