An initial geometry for a nacelle provides an intake at the upstream end of the nacelle and an exhaust at the downstream end of the nacelle. The intake has in flow series, an intake lip and a diffuser. The intake lip has a highlight defining the boundary between the inner and outer surfaces of the intake lip. On all longitudinal sections containing the axis of the engine (i) the inner and outer surfaces are tangency matched at the highlight, and (ii) the inner and outer surfaces have their maximum curvatures at the highlight.