Across:
   1,22. After his death 18 wept and knelt, jarring... I'm hurt terribly! (6 6 4, 2.)
   8. Improved mentoring required for killer of 1 across 22 (9)
   9. Words said for things seen during first halves - none unsaid! (5)
  11. Doctor, heal Mr. Gustav (6)
  12. Assaulter I order to provide a sort of extra motivation (8)
  14. What, with nous, PC is able to form about one (9)
  16. One part of play that's never right in screen adaptation (5)
  17. Some beef, raw drive, toppled tower over (5)
  19. Got down with "Dirty Deeds", in which many met end (9)
  21. Enough of one acquired deviously (with no internal revenue) before end of amnesty (8)
  22. see 1
  25. Plan on rejecting second compromise (5)
  26. One Tintin adventure will... (9)
  27. ...preserve Eastern Ocean with some sunshine around both sides, bringing end to 1 across 22 (5 4 3)
Down:
   1. Change of form with several couples leaving 5 city (7)
   2. Anger not right where 8 is to be used legally (5)
   3. Little bit backward describing first 9 letters (4)
   4. Start to learn one's welcoming lines, experienced in absence of friends (10)
   5. State reverse melody on trumpet when coming in before "C" heard (9)
   6. Learned to be true, die boldly! (7)
   7. Forty acres perhaps where milk and honey may be found (8 4)
  10. Giving up ringers under new scheme (12)
  13. 5 accuse 4, with energy and with bitterness (10)
  15. In sickness, lose head, hence sway (9)
  18. Novel aim: care for country (7)
  20. Appreciate louse taking last piece of my self-respect? (7)
  23. Core of main nerve bundle (5)
  24. Agitation and nasty riots after symbol of love killed (4)