The Bose polaron system consists of a Bose-Einstein condensate interacting with one, or few, impurities. Similar polaron models of particles interacting with a bulk system appear in many forms in condensed matter physics, and play an important role, e.g., for the understanding of transport properties. The topic of my talk will be the derivation of an effective equation starting from a dilute system of N>>1 interacting bosons and a single impurity. The effective description is given by the Bogoliubov-Fröhlich Hamiltonian, which couples the impurity linearly to Bogoliubov's excitation field in a similar way to other well-known polaron models. In the first part of the talk I will explain the main results and the underlying heuristics. In the second part I will focus on the key points of the rigorous derivation in connection with the renormalisation of the effective Hamiltonian. This is based on joint work with Arnaud Triay.