▁plan ▁in ▁the ▁United ▁Kingdom , ▁during ▁the ▁late - 1 9 9 0 s ▁and ▁early - 2 0 0 0 s . ▁ ▁The ▁first ▁was ▁an ▁update ▁to ▁a ▁small ▁number ▁of ▁ge ographic ▁di alling ▁codes ▁in ▁response ▁to ▁the ▁rapid ▁late - 1 9 9 0 s ▁growth ▁of ▁tele communic ations ▁and ▁imp ending ▁exhaust ion ▁of ▁local ▁numbers ▁in ▁several ▁cities . ▁The ▁change ▁greatly ▁expanded ▁the ▁pool ▁of ▁available ▁numbers ▁within ▁those ▁places ▁while ▁retain ing ▁' local ▁di alling ' ▁( the ▁ability ▁to ▁d ial ▁local ▁numbers ▁directly , ▁without ▁need ing ▁to ▁d ial ▁an ▁area ▁code ▁first ). ▁The ▁change ▁affected ▁the ▁di alling ▁codes ▁assigned ▁to ▁Card iff , ▁Cov entry , ▁London , ▁Northern ▁Ireland , ▁Port sm outh ▁and ▁South am pton , ▁cul min ating ▁in ▁a ▁large ▁switch ▁on ▁ 2 2 ▁April ▁ 2 0 0 0 . ▁All ▁of ▁these ▁places ▁moved ▁to ▁eight - digit ▁local ▁numbers ▁ens uring ▁sufficient ▁local ▁capacity ▁for ▁many ▁dec ades ▁( Lond on ▁saw ▁a ▁five - fold ▁increase ▁in ▁capacity , ▁for ▁example ). ▁No ▁other ▁ge ographic ▁area ▁codes ▁were ▁affected . ▁ ▁The ▁other ▁set ▁of ▁changes ▁affected ▁mobile , ▁non - ge ographic ▁and ▁prem ium ▁rate ▁numbers , ▁comple ting ▁a ▁series ▁of ▁steps ▁first ▁detailed ▁almost ▁a ▁de cade ▁earlier . ▁In ▁the ▁early - 1 9 9 0 s , ▁mobile , ▁non - ge ographic ▁and ▁prem ium ▁rate