It's from a sib cross over 15 years ago. It's a division of an old plant that just happened to be blooming. Actually this plant was from a seedling batch that included the much better known 'H&R Giant'. (so it's a sibling of HRG)
Even better versions have been carried on and bloomed with the 'H&R Giant' x 'H&R' or HRG self or outcrosses.