The present invention relates to a process for the production of polymers from waste plastics feedstocks comprising the steps in this order of: (a) providing a hydrocarbon stream A obtained by treatment of a waste plastics feedstock; (b) optionally providing a hydrocarbon stream B; (c) supplying a feed C comprising a fraction of the hydrocarbon stream A and a fraction of the hydrocarbon stream B to a thermal cracker furnace comprising cracking coil(s); (d) performing a thermal cracking operation in the presence of steam to obtain a cracked hydrocarbon stream D; (e) supplying the cracked hydrocarbon stream D to a separation unit; (f) performing a separation operation in the separation unit to obtain a product stream E comprising a monomer; (g) supplying the product stream E to a polymerisation reactor; and (h) performing a polymerisation reaction in the polymerisation reactor to obtain an polymer. The process of the present invention allows for optimisation of the quantity of waste plastic material that finds its way back into a polymer that is produced as outcome of the process.