prestel mailbox numbers were generally based upon the last 9 digits of the user's telephone number, without spaces or punctuation. for example, the prestel mailbox number for prestel headquarters which had the telephone number 01-822 2211 would be simply 018222211, while that for a user in manchester with telephone number 061-228 7878 would be 612287878. in keeping with the established telephone number practice, but unlike the convention with today's internet mailboxes, prestel mailbox numbers were published by default, and were available via the prestel computers in a dedicated directory accessible from page *486#. on request, "ex-directory" mailbox numbers were available, usually employing a dummy telephone number format such as the series 01999nnnn, and later the series 01111nnnn.