One of the more ambitious uses of intense microwaves in tokamaks or in other magnetic confinement deuterium-tritium (DT) fusion devices would be to divert power from energetic -particles to waves. This so-called `-channelling' would be a large step towards achieving economical fusion power. The intense waves, amplified by the substantial free energy in the -particles, damp on fuel ions, resulting in a hot ion mode, doubling the fusion power of the reactor at the same confined pressure. If the waves damp preferentially on electrons or ions travelling in one direction, current can be driven. This tutorial explains the key concepts and recent advances that lead us to believe in the plausibility of such an effect, at the same time showing how experiments to date give us a measure of confidence in both the simulations themselves, the underlying physical assumptions and ultimately the reasonableness of the application of these ideas to -channelling in a tokamak reactor.