  When the flavour content of QCD is increased sufficiently, the theory
develops a non-trivial infra red fixed point. Thus, for a number of flavours
above a certain critical value, but not yet so high that asymptotic freedom is
lost, QCD becomes a conformal field theory. The location of the lower limit of
this conformal window has not yet been unequivocally determined. Using an
improved lattice action, and exploiting modern algorithms allowing for larger
lattices and lower quark masses, we have shown that the theory of QCD with
eight flavours breaks chiral symmetry in the continuum. We present proof that
the accompanying transition is thermal in nature and as a consequence, the
conformal window of QCD can only start afterwards, corroborating recent
analytical studies at the expense of older results.
