Beautiful Invaders

I'm not entirely sure what this plant is, but it is currently covering the front lawn, as well as making inroads in to the fern bed and the flower bed on the roadside bank.  Its flowers are very pretty -- almost orchid-like, with delicate pale green veining on silvery white petals.  I think this is a form of wild garlic, but it doesn't smell particularly oniony.  They have been here longer than we have, but this year they seem to have outdone themselves.  The lawn mower will make short work of them soon enough.

Update:  A gardening friend has identified them as ornithogalum nutans, or "Nodding Star of Bethlehem".