A process for preparing an aqueous coating composition comprising a block copolymer and a polymer P; wherein the block copolymer comprises at least blocks x y, where at least block is obtained by a controlled radical polymerisation of at least one ethylenically unsaturated monomer via a reversible addition-fragmentation chain transfer (RAFT) mechanism; where block comprises: i) 0 to 50 mol% of ethylenically unsaturated monomer units bearing crosslinking functional groups; ii) 20 to 100 mol% of ethylenically unsaturated monomer units bearing water-dispersing functional groups; iii) 0 to 50 mol % of ethylenically unsaturated monomer units selected from linear or branched C 1 to C 8 alkyl (meth)acrylate monomers; iv) 0 to 5 mol% of ethylenically unsaturated monomer units bearing plastic adhesion promoting functional groups; and v) 0 to 10 mol % of ethylenically unsaturated monomer units different from those from i), ii), iii) + iv); where i), ii), iii), iv) + v) add up to 100 %; block has an average degree of polymerisation x, where x is an integer from 3 to 80; where block comprises: i) 0 to 5 mol% of ethylenically unsaturated monomer units bearing crosslinking functional groups; ii) 0 to 15 mol% of ethylenically unsaturated monomer units bearing water-dispersing functional groups; iii) 0 to 50 mol % of ethylenically unsaturated monomer units selected from linear or branched C 1 to C 8 alkyl (meth)acrylate monomers; iv) 20 to 100 mol% of ethylenically unsaturated monomer units bearing plastic adhesion promoting functional groups; and v) 0 to 10 mol % of ethylenically unsaturated monomer units different from those from i), ii), iii) + iv); where i), ii), iii), iv) + v) add up to 100 %; block has an average degree of polymerisation y, where y is an integer ≥ 10, where y > x; and where polymer P is obtained in the presence of the block copolymer by an emulsion polymerisation process, and comprises: i) 0 to 20 wt% of ethylenically unsaturated monomer units bearing crosslinking functional groups; ii) 0 to 15 wt% of ethylenically unsaturated monomer units bearing water-dispersing functional groups; iii) 50 to 100 wt % of ethylenically unsaturated monomer units selected from linear or branched C 1 to C 8 alkyl (meth)acrylate monomers; iv) 0 to 50 wt% of ethylenically unsaturated monomer units bearing plastic adhesion promoting functional groups; and v) 0 to 10 mol % of ethylenically unsaturated monomer units different from those from i), ii), iii) + iv); where i), ii), iii), iv) + v) add up to 100 %, where the ethylenically unsaturated monomer units bearing crosslinking functional groups i) are selected from the group consisting of hydroxyalkyl (meth)acrylates, glycidyl (meth)acrylates and diacetone acrylamide and mixtures thereof, where the ethylenically unsaturated monomer units bearing plastic adhesion promoting functional groups iv) are selected from the group consisting of isobornyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, dicyclopentenyloxymethyl (meth)acrylate, benzyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 3,3,5-trimethyl-cyclohexyl (meth)acrylate, p-methylphenyl (meth)acrylate, 1-naphtyl (meth)acrylate, 3-phenyl-n-propyl (meth)acrylate and 2-phenyl-aminoethyl (meth)acrylate, styrenic monomers, C 6 to C 20 optionally substituted alkyl(meth)acrylamide monomers, vinyl toluene, vinyl esters of versatic acid, vinyl chloride, vinylidene chloride and mixtures thereof, where polymer P is at least partially grafted to blocks, and wherein the aqueous coating composition is capable of being applied to plastic substrates to form a coating thereon, wherein the plastic substrate is polyolefinic, and wherein component iv) of block comprises at least 50 mol% of isobornyl (meth)acrylate. i) 0 to 50 mol% of ethylenically unsaturated monomer units bearing crosslinking functional groups; ii) 20 to 100 mol% of ethylenically unsaturated monomer units bearing water-dispersing functional groups; iii) 0 to 50 mol % of ethylenically unsaturated monomer units selected from linear or branched C 1 to C 8 alkyl (meth)acrylate monomers; iv) 0 to 5 mol% of ethylenically unsaturated monomer units bearing plastic adhesion promoting functional groups; and v) 0 to 10 mol % of ethylenically unsaturated monomer units different from those from i), ii), iii) + iv); i) 0 to 5 mol% of ethylenically unsaturated monomer units bearing crosslinking functional groups; ii) 0 to 15 mol% of ethylenically unsaturated monomer units bearing water-dispersing functional groups; iii) 0 to 50 mol % of ethylenically unsaturated monomer units selected from linear or branched C 1 to C 8 alkyl (meth)acrylate monomers; iv) 20 to 100 mol% of ethylenically unsaturated monomer units bearing plastic adhesion promoting functional groups; and v) 0 to 10 mol % of ethylenically unsaturated monomer units different from those from i), ii), iii) + iv); i) 0 to 20 wt% of ethylenically unsaturated monomer units bearing crosslinking functional groups; ii) 0 to 15 wt% of ethylenically unsaturated monomer units bearing water-dispersing functional groups; iii) 50 to 100 wt % of ethylenically unsaturated monomer units selected from linear or branched C 1 to C 8 alkyl (meth)acrylate monomers; iv) 0 to 50 wt% of ethylenically unsaturated monomer units bearing plastic adhesion promoting functional groups; and v) 0 to 10 mol % of ethylenically unsaturated monomer units different from those from i), ii), iii) + iv);