Big Number Change

The Big Number Change addressed various issues with the telephone dialing plan in the United Kingdom, during the late-1990s and early-2000s.

The first was an update to a small number of geographic dialling codes in response to the rapid late-1990s growth of telecommunications and impending exhaustion of local numbers in several cities. The change greatly expanded the pool of available numbers within those places while retaining '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. All of these places moved to eight-digit local numbers ensuring sufficient local capacity for many decades (London saw a five-fold increase in capacity, for example). No other geographic area codes were affected.

The other set of changes affected mobile, non-geographic and premium rate numbers, completing a series of steps first detailed almost a decade earlier. In the early-1990s, mobile, non-geographic and premium rate services had used nine digit numbers with various codes such as 0402, 0645, and 0898 scattered among the similar-looking geographic area codes such as 0384, 0562 and 0949. The number of available codes for new services was quickly dwindling. In 1995, PhONEday partially addressed this by altering all geographic area codes to begin 01, freeing up hundreds of codes beginning 02 to 09 for other uses. Existing mobile, non-geographic and premium rate services continued as before, using various codes from 02 to 09 and with nine-digit numbers.

In 1997 and 1998, mobile, non-geographic, and premium rate numbers started to be issued with ten digits and using only specific new prefixes: 070 for personal numbers, 076 for pagers, 077xx, 078xx and 079xx for mobiles, 0800 and 0808 for freephone, 0845 and 0870 for non-geographic revenue-share numbers and 090x for premium rate numbers. Within each of these groups some smaller number blocks were held aside for the older 9-digit mobile, non-geographic and premium rate services to move into at a later date. In 2000 and 2001, the Big Number Change put those final parts into place and they are detailed below.

At the end of the process, there were no numbers in the UK beginning 03, 04 or 06. Additionally, the 02, 05, 07, 08 and 09 ranges were only lightly used. With PhONEday in 1995 and the Big Number Change, the UK had achieved huge spare capacity for new services, and simple to understand prefix groupings: 01 and 02 for geographic numbers, 070 for personal numbers, 076 for pagers, 07624, 077, 078 and 079 for mobiles, 0500 and 080 for freephone, 084 and 087 for non-geographic and 090 for premium rate. Further new allocations would initially conform only to those groupings. Over the following decade, the 030, 033, 034, 037, 055, 056, 074, 075, 091 and 098 ranges would also come into use for new services or for further expansion of old services.

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