baɪ nˈaɪntiːnhˈʌndɹɪd sˈɪksti fˈaɪv, ðɛɹwˌɜː θɹˈiːhˈʌndɹɪd fˈɪfti lˈoʊkəl ɛkstʃˈeɪndʒᵻz ɪn lˈʌndən ænd ðə nˈʌmbɚɹ ʌv pˌɜːmjuːtˈeɪʃənz ðæt kʊd biː jˈuːzd fɔːɹ ɛkstʃˈeɪndʒ nˈeɪmz hɐdbɪn ɛɡzˈɔːstᵻd.
By 1965, there were 350 local exchanges in London and the number of permutations that could be used for exchange names had been exhausted.