Thanks for your reply.
I am aware of the contingencies you stated, so we are on the same page… but…
the discussion starts with the “interpretation” of when established of track, descend 500ft… and proceed as required until…
in my opinion, you theoretically could then immediately turn towards your diversion aerodrome, without descending below FL290.
other colleagues have a different opinion and say for diversion you need to descend below before you make that turn.