Rantzen founded Childline to help children in danger or distress after hosting a one-off programme, Childwatch, in which she asked viewers to open up about abusive childhoods.
He reprised the role in a series of films, as well as starring in cop show TJ Hooker and hosting 911 Rescue, a programme reconstructing real life emergencies.
Plymouth's role as the regional media capital would have been even stronger if ITV had not switched the hosting of its nightly news programme to Bristol - a result of the same pressures facing the newspapers.
But the demands of the new ICC programme have seen seasons stretched worldwide, with Zimbabwe hosting tours throughout their winter, and Sri Lanka taking July and August, despite it being the rainy season.
Members of the public have now been asked to comment on the castle's future which could see it hosting a more diverse all-year-round programme of outdoor festivals and events.