This project focuses on the development of new numerical modelling techniques for fatiguecrack growth and in particular, non-uniform crack front evolution and crack growth throughcomplex, through-wall residual stress profiles. Ultimately, the aim of the combined numerical-experimental research programme is to improve guidance in existing codes and standards (e.g. R6 and BS 7910) to reduce the potential over-conservatism of fracture mechanics andfitness-for-service assessments.