There is quite a power struggle going on in the upper reaches of Royal Dutch Shell. This week the FT revealed that four senior executives had left, or were leaving, adding that "several other top executives in the clean energy part of the business also plan to exit in the coming months." Outsiders cannot know exactly why they are going, and Shell's PR machine merely smoothed the usual guff about how wonderful everything is, but the battle lines are clear enough: is Shell an oil and gas company, or is it going to attempt the painful transition to a green energy business? That the transition would be painful is surely not in doubt. To displace the value of the hydrocarbons Shell produces today requires investment on an almost unimaginable scale. Many of the technologies needed are in their infancy, and the returns on investment highly uncertain, but almost certainly marginal.