PhONEday

A £16m advertising campaign, and an eight-month parallel period during which both old and new codes were active, preceded the change.

[1] PhONEday followed a change made in May 1990, when the old London area code 01 was released from use, permitting all United Kingdom geographic numbers to begin with this prefix.

On PhONEday, 16 April 1995, the digit "1" was added after the initial "0" to prefix all geographic area codes.

The changes made at PhONEday were one step towards reorganising the numbering plan at a later date, so that the first two digits would indicate the type of service called.

After PhONEday, all pre-existing 9-digit mobile, non-geographic, premium rate, personal and pager numbers from 02 to 09 remained in place.