Telephone numbers in the United Kingdom are administered by the Office of Communications (Ofcom). For this purpose, Ofcom established a telephone numbering plan, known as the National Telephone Numbering Plan, which is the system for assigning telephone numbers to subscriber stations.
The numbers are of variable length. Local numbers are supported from land-lines or numbers can be dialled with a '0'-lead prefix that denotes either a geographical region or another service. Mobile phone numbers have their own prefixes which are not geographical and are completely portable between providers.