Dust chicken pieces in flour. Heat oil in a flameproof casserole dish on high. Pan-fry chicken, in batches, for 2 minutes each side, until browned. Remove and set aside.
Reduce heat to medium. Add onion and garlic to pan and pan-fry for 3 minutes, until soft. Return chicken thighs to pan and add wine. Bring to boil. Simmer for 2 minutes, until wine almost evaporates.
Add passata and 1 cup water. Cover and simmer for 5 minutes. Add drumsticks and cook, covered, for another 5 minutes. Add remaining chicken and anchovies and simmer, covered, for 15 minutes, until cooked through. Stir through shredded basil and scatter over olives.
