In London, the national dialing code is 020. This is the number for most of Greater London, as well as nearby areas. The original dialing code for this area was 01 which was designated in 1959. During the 1990s, there were a series of changes. This resulted in the current 020 which was part of the Big Number Change. This last change happened in June of 1999.
All phone numbers in this area contain eight numbers. The code may be used on up to 100 million telephone numbers. Used on more than 170 telephone exchanges, the entire network is part of the United Kingdom’s biggest linking number scheme.
The 0 is used throughout the United Kingdom as the initial trunk prefix. The 0 in 020 is not required when someone is dialing into London from outside the United Kingdom.
https://www.net-telco.net is going to aware you about history of numbers-The first telephone exchange in London was called the Central which opened in March of 1902. This first exchange was created to allow Londoners to call others in the city. The first automatic exchange in London opened in 1927. This was mostly for businesses.
London had 134 exchanges by 1934 and all were located within 13 miles of Oxford Circus. By 1950, there were more than 235 exchanges located within the London metropolitan area. Heathrow’s exchanged opened in 1958.
The 020 code is used for the 20-kilometre area spreading out from the center of London. This area is larger than that served by the London post.
Eighteen London exchanges do not use this 020 code. They are mostly in six large boroughs which are located within other code areas.
Part of 32 boroughs around London and London City are served by the 020 number. Outside Greater London, there are another six exchanges using this code. These include Chigwell, Buckhurst Hill, Sewardstone, and Loughton.