Trajectory surface hopping was first discussed by Bjerre & Nikitin in 1967 as a semiclassical method to treat nonadiabatic dynamics, followed by a formal proposal by Tully & Preston in 1971. While many of the early studies employed simplified transition probabilities due to computational constraints (Landau-Zener approach) , numerous strides were made, before on-the-fly and generalised approaches were made available in many standard commercial software packages. Similar implementations by Xu and co-workers noted femtosecond deactivation rates for azomethane, while Cui & Thiel used a generalised surface hopping model to highlight ultra-fast internal conversion in acrolein on the femtosecond timescale.