Complete
00:00:00
8 10 13 16 6 5 19 1 17 2 9 14 3 11 15 4 12 18 7
  1. 5a Do for a happy couple, perhaps (9)
  2. 8a Written proposal or reminder (abbr) (4)
  3. 9a Unrealistic individual (8)
  4. 10a Insufficient in amount (6)
  5. 11a Plastic explosive (6)
  6. 13a Exude profusely (6)
  7. 15a Mean and moody? (6)
  8. 16a Weight (8)
  9. 18a Stepped (4)
  10. 19a Someone who presides over a forum (9)
  11. 1d Speak out against (8)
  12. 2d Frivolous behaviour (6)
  13. 3d By legend, the first 12 ended here (6)
  14. 4d End (one's own, perhaps?) (4)
  15. 6d Period when one is not at war (9)
  16. 7d No praises (anag) — disparaging comment (9)
  17. 12d Since 1921, the standard length for one of these has been 26 miles 385 yards (8)
  18. 14d Bring together (6)
  19. 15d Lose (6)
  20. 17d Sound of laughter (or disapproval) (4)