ABSTRACT The H-mode pedestal plays an important role in determining global confinement in tokamaks. In high triangularity H-mode experiments in Joint European Torus with the ITER-like wall (JET-ILW), significantly higher pedestal temperature and global confinement has been achieved with nitrogen seeding. The experimental increase of pedestal height is consistent with the stability calculations which show that edge localised impurity concentration can increase the electron pressure pedestal at the point of marginal stability. Numerically found stability improvement mechanism from impurity seeding is a combination of moving the pedestal inwards and increasing the ion dilution. Significantly better confinement and pedestal height have been observed in JET-ILW plasmas when the core pressure is increased. The enhanced pedestal height can be linked to an improvement in edge stability arising from an increase in the Shafranov-shift, higher edge current and pedestal widening in flux space.