The city, whose dialling code is 020, currently has 30 million phone numbers allocated across the existing (020)3, 7 and 8 ranges, Ofcom said.

The 913 and 316 area codes do not, which is why those area codes don’t have to adopt the new dialing standards. Phone systems will be switched on April 24 so that the 10-digit process for local ...

When area codes were first created in the 1950s, they had particular significance on a telephone dial. Numbers corresponded to two-letter identifiers, such as AB (22) for Aberdeen.