Across:
   5. Underground or underwater thoroughfare? (6)
   8. Plain gold coin? Yes! (8)
   9. He frees various confused characters (7)
  10. Contribution from idle nasty person under threat initially (5)
  11. They can barely run or steer arks (9)
  13. Ode I'd composed in Goa came from a brainwave (4 4)
  14. Take out a French advert (6)
  17. You can beat this urge! (3)
  19. Dad leaves pasty in pig-pen (3)
  20. Is she able to get here? (6)
  23. Against modelling after work (8)
  26. Second tax return leads to resentment in Norway (9)
  28. Force to travel round crest (5)
  29. Sacking the man who has a woman's name (7)
  30. Doctor works without interference or tears (8)
  31. Drunken lads in Australia? (6)
Down:
   1. Unable to find big fish outside (6)
   2. Dora holds suitable plug socket (7)
   3. Original sad tune in new arrangement (9)
   4. Rex, stop out at the wicket (6)
   5. Deploy Police ready for Dracula? (5 3)
   6. Quick! Here's a second chance! (5)
   7. Reforming a quasi-RU may be seen as a sign (8)
  12. Beat Brown? (3)
  15. Ideal material for ladders? (5 4)
  16. She serves Sir a stew (8)
  18. Denied putting profits before assistance (8)
  21. Called a halt to sorrow? (3)
  22. Sympathetic communist, or similar (7)
  24. Look around Spanish river for monastery (6)
  25. Fat King George has to move carefully (6)
  27. View is the best in Virginia (5)