John Dampier was a Leading Stoker who served aboard HMS Orontes during the Zulu War. HMS Orontes was a Royal Navy Troopship and was assigned to carry the body of the Prince Imperial from Simon's Bay back to England. Dampier is on the Medal Roll for "Orontes." He did not serve ashore with the Naval Brigade and could not have been injured in the Zulu War. He was invalided out of the service from "Orontes" on 11 August 1879 with a notation "unserviceable."
I don't have a copy of Dutton's book, but Dampier did not serve on HMS Forester. His service record does not show him having served aboard "Forester."