The UK telephone system has undergone a number of changes over the years to release capacity for the ever-expanding demand for new numbers. More changes are likely in the future. Some of the major changes are summarised below.
Newcastle-upon-Tyne (0632) with six-digit numbers became "Tyneside" with seven-digit numbers on (091). Numbers north of the river Tyne moved from (0632) xx xxxx to (091) 2xx xxxx and numbers south of the Tyne from (0632) xx xxxx to (091) 4xx xxxx. At the same time, the last exchange in the Newcastle "ring" (Ryton) was moved from (0894) to (091). As part of the same scheme, Durham numbers changed from (0385) xx xxxx to (091) 3xx xxxx, while Sunderland (0783) xx xxxx became "Wearside" on (091) 5xx xxxx.
London (01) was split into "inner London" on (071) and "Outer London" on (081).
A group of exchanges to the south of Bristol were split off from (0272) and included in (0275), a code previously used for the ring of exchanges surrounding Bristol..
All geographical codes changed from 0xxx to 01xxx, except that a group of cities which had reached number exhaustion was moved on to completely new codes, and changed from six-digit to seven-digit numbers:
Leeds moved from (0532) xx xxxx to (0113) 2xx xxxx
Sheffield moved from (0742) xx xxxx to (0114) 2xx xxxx
Notttingham moved from (0602) xx xxxx to (0115) 9xx xxxx
Leicester moved from (0533) xx xxxx to (0116) 2xx xxxx
Bristol moved from (0272) xx xxxx to (0117) 9xx xxxx
Later, Reading moved from (01734) xx xxxx to (0118) 9xx xxxx
Innner London moved from (0171) xxx xxxx to (020) 7xxx xxxx,
Outer London moved from (0181) xxx xxxx to (020) 8xxx xxxx.
Southampton moved from (01703) xx xxxx to (023) 80xx xxxx
Portsmouth moved from (01705) xx xxxx to (023) 92xx xxxx
Coventry moved from (01203) xx xxxx to (024) 76xx xxxx
Belfast moved from (01232) xx xxxx to (028) 90xx xxxx, while the rest of Northern Ireland moved from a multitude of codes to other (028) xxxx xxxx
Cardiff moved from (01222) xx xxxx to (029) 20xx xxxx
Potential Future Number Changes are now shown on a separate page