Renormalisation group (RG) techniques are currently used to derive relevant quantities in the vicinity of the critical point. The authors present a real space RG procedure which directly yields the order parameter for all values of the external parameters (e.g. temperature). It is as simple as a mean-field calculation, although it provides non-trivial results, which can be systematically improved. The method is successfully illustrated on the square lattice Potts ferromagnet. The whole approach suggests that the order parameter on a hierarchical lattice is, on every site, proportional to its coordination number.