A process for the preparation of a propylene homopolymer comprising polymerizing propylene in the presence of a catalyst comprising: (i) a metallocene complex of a group (IV) metal said metallocene comprising at least two cyclopentadienyl type ligands; (ii) a boron cocatalyst; and (iii) an aluminoxane cocatalyst; said catalyst being in solid form, preferably in solid particulate form, and being free from an external carrier; preferably wherein the melting point of the propylene polymer is controlled by adjusting the amount of or nature of the boron cocatalyst.