Well, I have limited experience with these plants, and I've never seen one that looks like that (photos or real life), but perhaps it's a Vesper Iris (Pardanthopsis dichotoma), which is crossed with Belamcanda (Blackberry Lily) to create the Candy Lily (Pardancanda)?
mmmmmm!! when I did a google and dogpile search for dietes grandiflora I came up with different pictures than MaVieRose's hyperlink. When I did the same for Neomarica gracilis, I came up up pictures that looked like Evert's hyperlinks. Also learned that a common name for Neomarica gracilis is walking iris.
If the author of the pic at MaVieRose's link has the name correct then surely that must be what it is. They look very much alike.
Regarding nomenclature, there are certainly some synonyms involved here.
I do know that 'Neomarica' was once called 'Marica'
This message was edited Thursday, Apr 11th 6:15 PM
Well, I totally missed the boat with my guess, but a websearch tells me that indeed Neomarica is a synonym of Dietes, as is Moraea. In fact, the websearches for the synonyms led me back to our own Plants Database more than once :)
My friends - don't get hung up on the naming of this plant. I would guess the taxonomists are sitting about in their research institutes laughing their socks off at the confusion they cause us mere gardeners. What I'm sure we do know is that it would make a nice addition to anyones garden or glasshouse.