Drop down cover means the unexhausted limit of the top layer of excess of loss cover drops down to a stated lower layer(s) to respond to further losses when that layer is exhausted. The reinsured uses a back up policy to cover the risk of the top layer itself being exhausted by an earlier loss. The risk can be mitigated by not combining too many layers in one top and drop arrangement when the total amount of cover is limited. Top and drop may be whole account or class specific. Dropping to the bottom of the programme is termed ‘cascade’. Top and step is a variation, the top layer only drops to reinstate the immediate underlying layer.