  Extending the SU(3) flavour symmetry breaking expansion from up, down and
strange sea quark masses to partially quenched valence quark masses allows an
extrapolation to the charm quark mass. This approach leads to a determination
of charmed quark hadron masses and decay constants. We describe our recent
progress and give preliminary results in particular with regard to the recently
discovered doubly charmed baryon by the LHCb Collaboration.
