Firstly, I have to commend you all for responding to my comment last week (which might not have been appreciated by all) as I have noted several tremendous attempts at "pushing the envelope" which regrettably in a few cases didn't quite dovetail into smooth surfaces or the wordplay couldn't be corroborated by accepted standards (Chambers primarily) but these efforts have very much been appreciated by me. In this category but definitely meriting mention are kt17's algebraic expression (I don't think 39 on its own is sufficient as a presidential indicator, paulhabershon's interest (coming from an actuarial background I know i is recognised as interest but not in crosswordland), tyke51's - as a disguised subtraction indicator and jono's odd/prime combo.
Other devices I like include kt17's topical Manchester (a) subtraction, paul's queen facing the wrong way & trance (I don't normally like straight anagrams but this was well written), chrise's initial replacement, faiton's "ent" and mathprofrockstar's (e) => (a).
My shortlist includes; buddy @4 & 23, dorrien @7, mattrom @ 11 and tyke51 @ 30. Those just falling short are fiery's Chaucerian jumble, buddy's &lit @ 9 and mattrom's spoonerism @ 29.
Bronze: peterm @ 22, not me! for can't :o)
Silver: BBM2 @ 20, a definite pdm when I finally deciphered red control - devious
Gold: aristo @ 12, it just flows delightfully
Hold off burning at the stake right after it starts to pour
I hope no-one's beliefs are offended,
https://youtu.be/WmMirk-2iiw
Again, many thanks to all who took part; I really appreciate the efforts clearly made in wordplay.