On exploring Google Book Search, I found a Rosemary Sutcliff short story. It's called Flowering Dagger and is in a collection called Within the Hollow Hills: an anthology of new Celtic writing, edited by John Matthews, published 2000 by Steiner Books. A few sample pages can be found here. It was originally published in The Real Thing, edited by Peggy Woodford, Bodley Head, 1977. Other contributors include: Robin Williamson, R.J. Stewart, Caitlin Matthews, David Spangler, Peter Vansittart, Henry Treece and Margaret Elphinstone, plus others.
Other books by or mentioning Sutcliff extracted on Google Book Search include: The Wanderings of Odysseus: The Story of "The Odyssey", Essential Fiction Genres Student Book by Peter Ellison, 100 More Popular Young Adult Authors: Biographical Sketches and Bibliographies by Bernard A. Drew, Honey for a Child's Heart: The Imaginative Use of Books in Family Life by Gladys M. Hunt, Killing the Celt by Tomas Runmhar, Black Ships Before Troy: the story of the Iliad, etc.