List of dialling codes in the United Kingdom
This is a list of telephone dialling codes in the United Kingdom, which adopts an open telephone numbering plan for its public switched telephone network. The national telephone numbering plan is maintained by Ofcom, an independent regulator and competition authority for the UK communications industries. This list is based on the official standard, but includes defunct codes and historical changes, including the derivation of the two letter identities, in cases where known. Dialling codes do not correspond to specific political boundaries: for example, the Coventry dialling code covers a large area of  Warwickshire and the Manchester dialling code covers part or all of several neighbouring towns. When dialling within the country, all area codes are preceded by the national trunk prefix 0, which has been included in all listings in this article. 0 was traditionally the number dialled for the operator for trunk calls before subscriber trunk dialling (STD) was introduced and so was retained as a prefix for direct-dialled calls. In the majority of areas, the area code still corresponds to the original STD letter code. When dialling from abroad, the 0 prefix is not dialled. When dialling within the  same area, the area code is not needed, save for a handful of areas that do require this. When calling from a mobile telephone, the area code is always needed. List of dialling codes. For an explanation of the two-letter STD codes used below, see Introduction of area codes. ELNS denotes Extended Linked Numbering Scheme areas, where an area code is associated with more than one place name. 01426, 01523 and other non-standard 01 prefixes were briefly used for pagers in the late 1990s and then moved to new 076 prefixes in the Big Number Change in 2000/2001 . The 01632 area code is set aside for use as fictional numbers for drama as are parts of a number of other area codes. Code length. The length of the area code part and the local number part is found as follows: The number format '2+8' refers to, e.g. London, numbers using the (020) xxxx xxxx format. The number format '5+4' refers to, e.g. Brampton, numbers using the (0169 77) xxxx format. Areas with mandatory area code dialling. In the following areas, the area code must be included when dialling local numbers. This enables local numbers  to start with 0 or 1 and was introduced to increase the number of available telephone numbers within these areas. Overseas Territories. Unlike the Crown Dependencies of Jersey, Guernsey and the Isle of Man which use the UK area codes 01534, 01481 and 01624, respectively, telephone numbers in British Overseas Territories do not come under the UK telephone numbering plan. Some are within the North American Numbering Plan (NANP). These calls are treated as international calls. Below are the access codes for the overseas territories: