Clients in particular can become litigious, and one of the key questions that arise is whether the risk of the client portfolio has been properly measured. To assess whether this is so requires the validation of the portfolio risk model. This area is virtually non-existent but has some features in common with Basel I. Thus, it is considered good practice to consider back-testing, scenario analysis and the like. Purveyors of risk models claim to test their products themselves, but they rarely make their models available for external validation. This means that the asset manager needs to take responsibility for the exercise.