This paper focuses on the study of the effect of the interfacial strength of grain boundaries and elliptical inclusions on crack path deflection. The method is developed to channel a crack into a toughening configuration (arrays of elliptical holes and inclusions are considered) in order to obtain the optimised microstructure required to enhance fracture toughness through different mechanisms. The proposed technique is shown to reproduce experimental crack propagation paths in various configurations and is capable of capturing the effect of that variation of the GB and the inclusion interfacial strength; it provides a powerful tool to understand the interplay between microstructural features and improve materials performance.