It's a Dietes. South African native. Tough as old boots and can be a weed in some areas. Often planted in the median strips of busy roads.

Yeah, I planted a heap of it once and eventually dug it all, or most of it, out. Not too difficult to remove but the clumps do thicken over the years and the thicker they get the tougher they are. It looks nice in flower and if its of any benefit, once established you never have to water it.
B.

It's not Dietes. It's one of the "walking Iris" - Neomarica candida. It's a beautiful plant though as many iris do, its flowers only last a day. But they do have flushes of flowering through the year (depending on your location). This one can be grown in a hanging basket as the strappy leaves hang down and flower from the ends, also and make new plantlets from the old flowering point.

Sorry, yeah, I have to agree with Alison, it is the 'Walking iris'; I also have that growing. It can spread, and spread and spread - arching tendrils that take root - especially in sub-tropical areas. As a matter of fact, I've just pulled heaps of it out, but not all; it does fill an empty space and the flower is nice.
B

Oops! Yes, my mistake. Alison is correct...

You caught us all out, Alison; teach me to respond to these questions after a glass or two of chardonnay as the sun is setting.
B.

such similar iris-type markings though, easy enough mistake to make when the sunset is in your eyes :-)
True what you said about dietes though, Bill, very hardy plant, if we don't get any rain soon I may just spread 'em round the yard, they seem to be one of the few survivors.

Ha ha, thanks for being kind Alison, but shame on me for responding too impulsively. They are as you say, tough as old boots; and, when you've a group them in flower, they do catch your eye. And if they get too thick they're not too difficult to thin out.

B.