Dual citizenship (also known as dual nationality) is allowed in the UK. This means you can be a British citizen and also a citizen of other countries.
If you are a British national of Italian descent, learn if you qualify for Italian dual citizenship and continue to be part of the EU. More HERE.
Married couples often want to apply for their Italian dual citizenship at the same time, even if only one of them is qualified for citizenship jure sanguinis. In order for a spouse to apply through marriage, the couple must first be married three years and one spouse has to have Italian citizenship.