  We study the role of Chern--Simons couplings for the appearance of enhanced
symmetries of Cremmer--Julia type in various theories. It is shown explicitly
that for generic values of the Chern--Simons coupling there is only a parabolic
Lie subgroup of symmetries after reduction to three space-time dimensions but
that this parabolic Lie group gets enhanced to the full and larger
Cremmer--Julia Lie group of hidden symmetries if the coupling takes a specific
value. This is heralded by an enhanced isotropy group of the metric on the
scalar manifold. Examples of this phenomenon are discussed as well as the
relation to supersymmetry. Our results are also connected with rigidity
theorems of Borel-like algebras.
