æz pˈɑːɹt ʌvðə bˈɪɡ nˈʌmbɚ tʃˈeɪndʒ ˌɔn twˈɛnti tˈuː ˈeɪpɹəl tˈuː θˈaʊzənd, ðə zˈiəɹoʊwˈʌnsˈɛvənwˈʌn ænd zˈiəɹoʊwˈʌnˈeɪtwˈʌn kˈoʊdz wɜː ɹᵻplˈeɪst wɪð zˈiəɹoʊ twˈɛnti, fˈɑːloʊɪŋ ɐ pˈiəɹɪəd ʌv dˈuːəlɹˈʌnɪŋ ðæt bɪɡˈæn ˌɔn wˈʌn dʒˈuːn nˈaɪntiːnhˈʌndɹɪd nˈaɪnti nˈaɪn wɛn ðə nˈuː zˈiəɹoʊ twˈɛnti kˈoʊd wʌz ˈæktᵻvˌeɪɾᵻd ænd ˈɛndᵻd ˌɔn fˈoːɹtiːn ɑːktˈoʊbɚ tˈuː θˈaʊzənd wɛn ðɪ ˈoʊld zˈiəɹoʊwˈʌnsˈɛvənwˈʌn ænd zˈiəɹoʊwˈʌnˈeɪtwˈʌn kˈoʊdz wɜː fˈaɪnəli sˈiːst.
As part of the Big Number Change on 22 April 2000, the 0171 and 0181 codes were replaced with 020, following a period of dual-running that began on 1 June 1999 when the new 020 code was activated and ended on 14 October 2000 when the old 0171 and 0181 codes were finally ceased.