  We assess the energy limit up to which Heavy Baryon Chiral Perturbation
Theory (HBChPT) can be applied to the process of neutral pion photoproduction
from the proton by analyzing the latest data collected by the MAMI/A2
collaboration at Mainz. The high-quality differential cross section and the
photon asymmetry measured data allow to test the theory at a level not
previously achieved. We find that, within the current experimental status, the
agreement between theory and experiment is excellent up to $\sim$170 MeV. Above
this energy HBChPT fails to provide high-quality fits while an empirical
parametrization of the multipoles still provides an excellent description of
the data.
