One of the main results of [2] shows that neither the Weyl algebra An, nor any (Lie Algebra) quotient of A can be realised as analytic vector fields on a finite dimensional manifold. In this note we give an elementary proof of this fact. This is related to the non-existence of finite dimensional recursive filters for certain problems in non-linear filtering theory, notably the cubic sensor problem (see [2,3 and 4]). The methods used here also show that the Weyl algebra has no sub-Lie algebra of finite codimension.