Two interlinked and complex problems face energy policy-makers: future energy supplies and climate change. The choices made on energy mix will lock development pathways for some considerable time ahead. Climate change is a challenging problem. Decarbonising the energy system requires sustainable and environmentally friendly technologies that work within the context of the planetary environment and do not cause “collateral damage”. Several approaches are available. But nuclear power is an unsustainable technology that has already caused “collateral damage” and will leave a toxic legacy of waste, for which there appears to be no solution. Including nuclear in a future energy system is a step in the wrong direction.