A bank which has obtained the Agency's approval for the use of one or more models will no longer be able to revert to measuring the risk measured by those models according to the standardised methodology (unless the Agency withdraws its approval for the model(s), as explained in section CA-9.9). However, what constitutes a reasonable period of time for an individual bank which uses a combination of internal models and the standardised methodology to move to a comprehensive model, will be decided by the Agency after taking into account the relevant circumstances of the bank.