Paul, I would consider this an Allium senescens hybrid. This species so readily hybridizes with other rhizomatous alliums, that much of what one sees in cultivation, and certainly many seed-grown plants, are best characterized as A. senescens hybrids. In your plant, the foliage is more narrow than normal, and the inflorescence looser and slightly fewer-flowered than normal, but otherwise it's a ringer for Allium senescens.
