comedy series Birds of a Feather. At the time of the split, there were five local exchange codes assigned to Mercury Communications and numbers in these ranges could be assigned to either code. This area code split doubled the potential capacity. In 1995, on "PhONEday", the codes changed again, to 0171 and 0181. The split into two area codes only lasted a decade. As part of the Big Number Change on 22 April 2000, the 0171 and 0181 codes were replaced with 020, following a period of dual-running that began on 1 June 1999 when the new 020 code was activated and ended on 14 October 2000 when the old 0171 and 0181 codes were finally ceased. The 22 April 2000 change also affected subscriber local numbers which gained an extra digit. "0171-xxx xxxx" numbers changed to "(020) 7xxx xxxx", while "0181-xxx xxxx" numbers became "(020) 8xxx xxxx". As a result of this history, there is now a widespread misconception that 0207 and 0208 are the dialling codes for parts of London. This was exacerbated when local numbers beginning 3 started to be issued. The reunification under a single code created capacity for approaching 100 million telephone numbers and, starting in 2005, subscriber numbers beginning with the digit "3" were issued alongside those beginning "7" and "8". In August 2019, Ofcom announced that subscriber numbers beginning with the digit "4" will also be introduced. Charge group The London telephone area operated as a single group for charging purposes in which all calls were priced at local rate. Additionally, as was usual, calls to and from the adjacent charge groups were charged as local. Coverage The code serves a roughly circular area with a radius of from the centre of London. The Greater London boundary varies from to from the centre and consequently some outer districts are covered by adjacent codes and in some places the 020 code extends beyond the Greater London boundary. The code covers an area larger than the London post town where letters addressed to "LONDON" are delivered. The City of London and at least some part of all 32 London boroughs are within the 020 area code. There are six exchanges outside Greater London that use the 020 code. Communities outside Greater London that are within the code are Buckhurst Hill, Chigwell, Loughton and Sewardstone in Essex; Borehamwood, Bushey, Carpenders Park, Elstree and South Oxhey in