Models are an integral part of modern banking. They are used inter alia to price transactions, value portfolios and optimise returns. They are also a key cornerstone of the regulatory framework, used to determine required capital and liquidity. In this paper, we set out the key cornerstones of a modern model risk management framework. We start with an overview of the regulatory (i.e., mandatory) requirements, but then consider in greater detail other aspects of the framework, in particular those where some element of management discretion remains.