ɪn ˈɔːɡəst tˈuː θˈaʊzənd nˈaɪntiːn, ˈɑːfkɑːm ɐnˈaʊnst ðæt səbskɹˈaɪbɚ nˈʌmbɚz bɪɡˈɪnɪŋ wɪððə dˈɪdʒɪt "fˈoːɹ" wɪl ˈɔːlsoʊ biː ˌɪntɹədˈuːst.
In August 2019, Ofcom announced that subscriber numbers beginning with the digit "4" will also be introduced.