The future of the global economy once again rests on an 100-mile strip of water sandwiched between the Persian Gulf and the Sea of Oman. Shipping through the vital waterway has halved following tit-for-tat strikes between the US and Iran this week, shaking the foundations of a sketchy 14-point interim peace deal between the warring nations. It started when Iran attacked three commercial vessels passing through the Omani corridor of the Strait of Hormuz in overnight attacks on Monday.