We took the difficult decision to go to the nest and remove both the dead chick and the one that was barely alive and try and feed it. After around 15 minutes we finally got him to take some fish. He/she was shaking and could not lift it's head. After around 30 minutes we had its crop around half full and he had stopped shaking - we immediately put him back in the nest and around 5 minutes later Nora was feeding him.
Intervention like this is not the norm and will, most likely, attract some criticism. At the moment, we feel we had no option but to intervene in this way.
Nora sitting on the nest
Video before the storm and the loss of one of the chicks