50.

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Across
  1. 3. WELL Painting proficiently could be source of fortune (3,4)
  2. 5. Source of inspiration for Keats
  3. 8. Flooded area used to be source of hope (5)
  4. 10. Small wines turn out to be sources of strength (6)
  5. 11. Sources of inspiration for a painter say
  6. 12. School has expert around to be source of solution (7)
  7. 14. Provide inspiration for puzzle (6)
  8. 17. MAN LUNG Source of inspiration for Arthur Curry?
  9. 18. Composer interrupting historian may be source of distress in hospital (7)
  10. 19. Admit home help for puzzle solvers will get 500 entering (7)
Down
  1. 1. Seafood said to be source of strength (7)
  2. 2. Fish around Isle of Man may be source of energy (7)
  3. 4. Savvy about new place for puzzle (7)
  4. 6. Tools for puzzles (7)
  5. 7. ONES GOAT Be source of annoyance
  6. 9. TREE Source of inspiration for Sir Isaac Newton, famously
  7. 13. Bare gum may be source of irritation
  8. 15. Be sources of inspiration for puzzles (7)
  9. 16. 15th-century author and "knight prisoner" whose Le Morte d'Arthur was the source of inspiration for T. H. White's The Once and Future King tetralogy (6)
  10. 18. Military units that can be sources of power