  We analyse and numerically simulate the full many-body quantum dynamics of a
spin-1 condensate in the single spatial mode approximation. Initially, the
condensate is in a ``ferromagnetic'' state with all spins aligned along the $y$
axis and the magnetic field pointing along the z axis. In the course of
evolution the spinor condensate undergoes a characteristic change of symmetry,
which in a real experiment could be a signature of spin-mixing many-body
interactions. The results of our simulations are conveniently visualised within
the picture of irreducible tensor operators.
