Quicksmiths (hard)

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Across
  1. 4. The study of puzzles (9)
  2. 6. Eartha's statue is in this courtyard, named after an Ancient Egyptian mathematician (7)
  3. 7. Leela says Timmi is one of these because she has a lot of Quickets (13)
  4. 10. The Head Librarian (3,3)
  5. 12. The outdoor theatre is named after this Ancient Greek philosopher (9)
  6. 13. The mowl collects these (10)
  7. 15. Ambassador A's real name (6)
  8. 17. Name of Thag's ancestor (7)
Down
  1. 1. Scaleface is one of these (7)
  2. 2. Stops you talking about Strange Energy and Quicksmiths(13)
  3. 3. The third riddle is found on this (6)
  4. 5. The old oak is in this courtyard, named after an Ancient Chinese philosopher (9)
  5. 8. The park where Kip plays chess (9)
  6. 9. Name of the drones fixing the Clock Tower (6)
  7. 11. The aquarium shop is on this avenue (5)
  8. 14. Timmi's full first name (8)
  9. 16. From riddle no. 4 'Reverse Time's _ _ _ _ _' (5)