Had a go on Facebook about the above and had loads of replies from sundry crew chiefs, riggers, sooties etc, plus a few aircrew. Quite surprised how many had never heard the term, particularly those from the latter days of the K2s, by which time the nickname seems to have fallen into disuse. A lot on the other hand said they always knew it as Annie's hatch.
Only one problem - nobody had a clue who Annie was!