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.