Big Number Change

The Big Number Change was an update of telephone dialling codes in the UK in response to the rapid late-1990s growth of telecommunications and impending exhaustion of numbers. The change greatly expanded the pool of available numbers while helping to retain 'local dialling' (the ability to dial local numbers directly, without needing to dial an area code first). The change affected the dialling codes assigned to Cardiff, Coventry, London, Northern Ireland, Portsmouth and Southampton, culminating in a large switch on 22 April 2000. In addition to new area/city codes for many parts of the UK, the switch was also coupled with a move to eight-digit local numbers, the adjustment of all mobile phone numbers in the UK to the 07 prefix and the alteration of many non-geographic codes to the new 08 range.

All of the above areas now have an eight-digit local number, in place of their previous six or seven-digit local number. For a short while you could use either number for local dialling, but local access to the old, shorter, numbers was switched off after a few months of parallel running.

In London, new 70xx xxxx, 71xx xxxx, 80xx xxxx, and 81xx xxxx numbers became available for general use. These began to be allocated anywhere in London, with no regard for the 1990-2000 inner/outer London geographical split.

In all of the other areas, new ff0x xxxx and ff1x xxxx numbers became available for general use at the same time (where ff is '76' in Coventry, '20' in Cardiff, etc).

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Northern Ireland

County Antrim

County Armagh

County Down

County Fermanagh

County Londonderry

County Tyrone

Belfast area

All this meant that while Enniskillen's numbers could be six digits long, Kesh's and Lisnaskea's (and those of other dependent exchanges) could only be five digits, due to the limit of the length of a phone number. This severely restricted capacity in these areas. As a result, at the Big Number Change, all these dependent exchanges were migrated to different numbers than their parent exchanges; in this instance while Enniskillen's 01365 (the 1 coming from PhONEday) was migrated to 028 66, Kesh went from 013656 to 028 686 and Lisnaskea from 013657 to 028 677. This meant that Kesh could expand into the rest of the 028 68xx range.

Note that the new numbering scheme groups numbers together such that the first digit identifies the county in alphabetical order. The exception is the Greater Belfast area where all numbers begin with 9, regardless of the county. The full list of changes for Northern Ireland^{[ 2} is as in the table above.

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National dialling only ranges

In London, old National Dialling Only 0xx xxxx and 1xx xxxx numbers were migrated to new 0axx xxxx and 1axx xxxx numbers (where 'a' is mostly 0 or 1, so far).

In all of the other areas, old National Dialling Only 0xxxxx and 1xxxxx numbers were migrated to new 0aax xxxx and 1aax xxxx numbers.

These migration from old to new numbers was as follows:^{[ 2}

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Mobile numbers

The following changes were made to mobile phone numbering ranges to bring them in the 07xxx mobile numbers range.

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Pager numbers

The following codes for pager numbers were also changed, so that all are in the 076xx range:

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Numbers for drama

These fictional numbers are made available by Oftel for dramatic purposes, for example for quoting in TV, radio and film. Oftel explains: "Telephone Numbers recommended for drama purposes cannot be allocated to Communications Providers for their customers because of the potential influx of calls that customers may receive should their Telephone Numbers be shown in a drama."^{[ 4}