The deal just signed by Sir John Browne, chief executive of BP Amoco, could revolutionise the energy business. The decision on April 6th to spend $45m to win control of Solarex. This will BP the world's biggest solar-energy company. Despite its trifling size, the deal raises interesting questions about the thinking of its mastermind. Sir John runs the world's second biggest oil company. Ye the man who has made a name for himself as a ruthless cost-cutter and daring deal maker now seems to be behaving like a quixotic dreamer. Solarex is not the only example. Sir John is pushing ahead with other environmentally friendly schemes.