Justice is a liberty, not a choice

A British citizen has a right of abode and is not subject to any immigration restrictions in the UK. There are two ways to become a British citizen under British nationality law, through naturalisation or registration, depending on your immigration status in the UK or nationality. Each category has different requirements. You do not need to renounce your existing citizenship to become a British Citizen unless you are a national of a country which does not allow dual nationality.