text: Telephone numbers in the United Kingdom are administered by the UK government's 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. Since 28 April 2001, almost all geographic numbers and most non-geographic numbers have 9 or 10 national (significant) numbers after the "0" trunk code. All mobile telephone numbers have 10 national (significant) numbers after the "0" trunk code. The overall structure of the UK's National Numbering Plan is: A short sample of geographic numbers, set out in the officially approved (Ofcom) number groups: In the United Kingdom, area codes are two, three, four, or, rarely, five digits long (after the initial zero). Regions with shorter area codes, typically large cities, permit the allocation of more telephone numbers as the local number portion has more digits. Local customer numbers are four to eight figures long. The total number of digits is ten, but in a very few areas the total may be nine digits (after the initial zero). The "area code" is also referred to as an "STD (code)" (subscriber trunk dialling) or a "dialling code" in the UK.