KMnF3 perovskite undergoes 3 structural, and two magnetic phase transitions on cooling from 300 K to 2 K. Above 185 K the compound is in the aristotype structure, on cooling below 185 K it undergoes a weakly first order zone boundary phase transition to a structure in space group I4/mcm with Glazer symbol a0a0c-. At the Neel temperature (87 K) it undergoes a second weakly first order transition to an as yet uncharacterised phase, probably space group Cmcm. At 82 K it undergoes a second magnetic/structural transition to another uncharacterised phase, probably in space group Pnma. We propose to carry out a full structural and magnetic characterisation of the 4 phases of KMnF3 including the evolution of the spontaneous strains and the nature of the phase coexistence in the first order transitions on heating and cooling.