There are two different ways in which calls from UK numbers can be identified. The effectiveness of using the 141 prefix depends on which is being used.
There is a difference between
- the identity of the calling line, which can be withheld (e.g. by using 141 as a prefix)
and
- the "location data" covering the geographical position from where the call was made, which may be freely used.
This is all covered, in somewhat formal language, by the
Privacy and Electronic Communications Regulations (2003).
The relevant regulations are numbers 10, 12 and 14. The definitions at part 2 are helpful, as are the "explanatory notes".
I quote below the essence of regulations 10 and 14.
Quote:The provider of a public electronic communications service shall provide users originating a call by means of that service with a simple means to prevent presentation of the identity of the calling line on the connected line as respects that call
Quote:data indicating the geographical position of the terminal equipment of a user of a public electronic communications service may be processed where that user or subscriber cannot be identified from such data
It has been noted that some call originators fail to provide proper location data, on which calls to many services rely. This is not necessarily a good thing, but it may provide a means of getting around the block on UK originated calls which some apply to their "overseas only" numbers.
Where such blocks are applied, it is important to establish whether there are genuine service reasons for doing this, or if it amounts to an admission that the revenue from calls to 084 numbers is sufficiently important to the organisation as to require the deployment of techniques to protect it.