In addition to the number of botanicals (ten) that leads to its complex flavor, a distinguishing factor of Sapphire is the method by which said botanicals are infused into the spirit.
Rather than boiling the botanicals in the spirit, during the distillation process the spirit vapors are passed through a copper basket containing the botanicals. This more gentle infusion maintains the subtleties of each flavor.
Mmm, Sapphire.
www.bombaysapphire.com has a lovely movie of the process