On a more serious note, although only guidance, and there is no obligation for people to adopt any particular solution contained in an Approved Document if they prefer to meet the relevant requirement in some other way, there is undoubtedly the presumption in Approved Document P that P1 will be complied with by adhering to BS 7671: 2001.
And the actual Building Regulations defines one of its terms by referring to a definition in BS 7671: 2001 incorporating amendments 1 and 2.
Neither document has been updated.
Also, I've recently applied for Building Regs approval for an extension, and the guy who drew up the plans and submitted the application said that "All wiring and electrical work to be designed, installed inspected and tested in accordance with the requirements of BS7671, the IEE 16th edition..."
When I pointed out that this was unlikely, as approval was only granted at the end of May and we haven't even found a builder yet, his response was that we only have to work to the regulations in force when the approval was granted - we've got 3 years to start the work, and all sorts of things could change, but they don't apply to approvals already granted....