Generation of an "unnatural" helical polymer, i.e., a poly(isocyanide) with side chains of identical absolute configuration to the "natural" one but with a helical secondary structure of opposite handedness, is reported. It is demonstrated that the natural tendency of promesogenic monomer to form poly(isocyanide)s of predominantly one helical sense is not a cooperative process. Rather their secondary structure is trapped during formation through long-range chiral induction. Using a kinetic trick the growth of these "natural" helices can be blocked, allowing the "unnatural" poly(isocyanide) to form in preference.