Abstract: The invention relates to a process for the preparation of a polymer comprising monomeric units of ethylene, an ?-olefin and a vinyl norbornene applying as a catalyst system: a. a bridged or an group 4 metal containing an unbridged catalyst having a single cyclopentadienyl ligand and a mono substituted nitrogen ligand, wherein said catalyst is defined by the formula (I): b. an aluminoxane activating compound, c. 0-0.20 mol per mol of the catalyst of a further activating compound, wherein Y is a substituted carbon or nitrogen atom. The invention further relates to a polymer obtainable with the process of the invention.