Mallard Record Brood ?

I spotted a female Mallard with 18 newly hatched ducklings this morning on the canal. This must be an exceptional sized brood even for Mallard ? When I spotted all the ducklings I assumed there were a couple of broods mixed together but only one female was present and she was definitely caring for the whole brood. I forgot the camera this morning but will try and get a shot of them tomorrow assuming they all survive overnight.