<Table> <Tr> <Td> </Td> <Td> This article appears to contradict the article Telephone numbers in the United Kingdom . Please see discussion on the linked talk page . (May 2012) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article appears to contradict the article Telephone numbers in the United Kingdom . Please see discussion on the linked talk page . (May 2012) (Learn how and when to remove this template message) </Td> </Tr> <P> In the UK, letters were assigned to numbers in a similar fashion to North America, except that the letter O was allocated to the digit 0 (zero); digit 6 had only M and N. The letter Q was later added to the zero position on British dials, in anticipation of direct international dialing to Paris, which commenced in 1963 . This was necessary because French dials already had Q on the zero position, and there were exchange names in the Paris region which contained the letter Q . </P> <P> Most of the United Kingdom had no lettered telephone dials until the introduction of Subscriber Trunk Dialing (STD) in 1958 . Until then, only the director areas (Birmingham, Edinburgh, Glasgow, Liverpool, London and Manchester) and the adjacent non-director areas had the lettered dials; the director exchanges used the three - letter, four - number format . With the introduction of trunk dialing, the need for all callers to be able to dial numbers with letters in them led to the much more widespread use of lettered dials . The need for dials with letters ceased with the conversion to all - digit numbering in 1968 . </P>

When did they use 4 digit phone numbers