Or at least it was sold under this name ("Cnths speciosa" is not in Kew). In IOSPE it looks like Cnths guianensis ( IOSPE PHOTOS ). Any guess?
A single flower, with a strong fragrance; the 'white' is so bright that reflects the flash light, so the pics don't show the real color (lavander blue?)
I have one identified as "candida", not bloomed yet; the plant size is different ("candida" is smaller), but it's not a criterion (it can be still young!). When the little "candida" bloom, not only the flower - shape and colors, but the fragrance (very strong in this "speciosa"!) will tell me the truth!