It seems that ISO 3166 has been changed so that it is now consistent with the DNS: Jersey, Guernsey, the Isle of Man, and the UK now have their own country codes and are no longer bundled together in the catch-all “GB”. This means that the GBR annotations in my passport are obsolete.
RIP ftp.dra.hmg.gb.
Link: http://www.circleid.com/posts/gg_im_je_iso3166_good_bye_gb/