For this crossword all down clues are normal and entered normally in the grid. All but four of the across clues must be altered before entering them in the grid. The remaining four across clues contain extra letters in the wordplay which, when put together, provide the means of altering the other across answers.
All grid entries are real words.
To get the tick the answer must show the completed grid and explain the means of modifying the across entries correctly.
Across: 1. Reorganised menu with no new bird(3) 5. That woman, this place… interminable!(3) 8. Processed bull leads to bovine encephalitis entering farms(4) 9. Three-eighths of esoteric furniture arranging needs Chinese money(3) 10. Purchase unpopular agreement (3) 11. Small ornamental case found in Louvre-Tuileries complex (4) 12. Notion of animalistic part of self has bum (4) 13. Space in old dry canvas shelter (4) 15. Record headgear holds 35 litres for Moses (4) 19. Nine and one, a decade for South African Iris (4) 21. What was done to convey rights (4) 22. This is how cows usually digest at first (3) 23. Put awkward boat back however (3) 24. Sifu Jinshu possesses Honshu mountain (4) 25. Mix tonic-water without carotin - it's this (3) 26. Visionary, if eyes can hold it (3) DOWN: 1. Popular song from years ago – time-worn, that is (5) 2. Uncultivated land has trees left for nothing (4) 3. Write letter between articles in Samoan city (4) 4. Locate spatter region (4) 5. They said he propelled a boat, but he was on a horse (4) 6. Nil-ten and opponents form a draught team (4) 7. Transport marble head without getting tense (3) 14. Stair breaks ankle bones (5) 16. Juan's chicken? Heartless but game! (4) 17. Was optimistic before Papa went cultivated (4) 18. Horny without right man (4) 19. Shortchanges (no Special K!) children?(4) 20. Headless horse has a position within… (4) 21. …an inferior horse can annoy continually (3)