The world’s largest financial institutions have thrown their carefully-drawn dealmaking playbooks to the wind and submitted to the direction of government regulators, sparking a wave of convoluted and unpredictable merger activity.

“Rescue” deals to prevent or soften the collapse of institutions including Merrill Lynch, Wachovia and Fortis have redrawn the banking map in a breathtakingly short time. In high-stakes situations ideas and structures that had never been tested – or even fully conceived – have suddenly been put into practice.