No idea....could it be some sort of Bromeliad ? God knows which one...Bilbergia ? Neoregalia ? Guzmania ?

It's fasicularia bicolor, a relative of the pineapple.

Both right - fasicularia bicolor, which is a Bromeliad.

And supposedly reasonably hardy.

Thank you all, been trying to find it on the web for weeks with no luck.

Very true Owdboggy. Mine has been growing in the garden, sheltered by a tree, for eight years.

Last week I was reading an article that said it would grow under hedges in the shade. (Written by head gardener at a local stately home)