British telephone numbers will require new dialing codes beginning today.
Most of the new area codes will simply add a numeral 1 in front of the existing code when it is dialed from outside the country.
London’s two previous codes - 71 and 81, will now be 171 and 181.
Inside the country, the codes are preceded by a 0; in London that was 071 and 081. Now they will be 0171 and 0181.
Five cities - Bristol, Leeds, Leicester, Nottingham and Sheffield - have entirely new codes.
Callers using the old code will hear a recorded announcement telling them how to redial using the correct code.