We characterize all internally 4-connected binary matroids M with the property that the ground set of M can be ordered (e0, . . . , en-1) in such a way that {ei, . . . , ei+t} is 4-separating for all 0 i, t n - 1 (all subscripts are read modulo n). We prove that in this case either n 7 or, up to duality, M is isomorphic to the polygon matroid of a cubic or quartic planar ladder, the polygon matroid of a cubic or quartic M