  We consider the quantum quench in the XX spin chain starting from a tilted
N\'eel state which explicitly breaks the $U(1)$ symmetry of the post-quench
Hamiltonian. Very surprisingly, the $U(1)$ symmetry is not restored at large
time because of the activation of a non-Abelian set of charges which all break
it. The breaking of the symmetry can be effectively and quantitatively
characterised by the recently introduced entanglement asymmetry. By a
combination of exact calculations and quasi-particle picture arguments, we are
able to exactly describe the behaviour of the asymmetry at any time after the
quench. Furthermore we show that the stationary behaviour is completely
captured by a non-Abelian generalised Gibbs ensemble. While our computations
have been performed for a non-interacting spin chain, we expect similar results
to hold for the integrable interacting case as well because of the presence of
non-Abelian charges also in that case.
