This is a list of dialling codes for telephones in the United Kingdom. Dialling codes are the basis for the national telephone numbering plan. They are prefixed to all telephone numbers, generally depending on the type of number and its geographic location. The numbering plan is maintained by Ofcom, which is an independent communications authority. This list is based on the official standard, but it also shows older codes and historical changes. Dialling codes do not match any specific political boundaries. For example, the dialling code for Coventry covers a large area of Warwickshire and the Manchester dialling code covers part or all of several neighbouring towns. When dialling a number from within the United Kingdom, all area codes start with a 0. When dialling from outside the country, the prefix is not dialed.