What is this plant with purple cherry-shaped fruit?

Question

I came across this beautiful plant in a botanical garden - what could it be?

Answer 1

Well they look like Leycesteria formosa berries, but there's no foliage which even remotely resembles that plant in your picture. Is the stem with the berries actually coming from the sword like leaves in your picture, or is just trailing across them from somewhere else? If the stem IS coming from the clump of leaves, then its Dianella caerulea or Dianella tasmanica

http://www.ozbreed.com.au/strappy-leaf-plants/tasred-dianella-tasmanica-tr20.html