"United Kingdom, British Overseas Territories and Crown dependencies
There is no "official language" of the United Kingdom - meaning that any language may be used to in the course of business or legal proceedings. Generally a contract is valid and binding regardless of the language in which it was made. English however is most commonly spoken and written, with several regional languages having been awarded special legal designation.
In England almost all legislation is written in English, however some older statutes are in Latin.
Cornish has been officially recognized as a language of cultural importance. It is not however an "official language" any more than is any other language.
British Overseas Territories
Isle of Man