It is a common misconception that London still has more than one area code (i.e. "0207", "0208" and even the later "0203", which was the pre-1995 code for Coventry followed by 0204). This is incorrect in the sense that omitting the "0207" or "0208" (area) code will give a local number that cannot be connected as it is missing the first digit. Therefore, writing a London number as 020x xxx xxxx is incorrect and can lead to confusion when attempting to dial it.
