Prince Charles has revealed how proud he is of his son, Prince Harry, for embracing his concerns about climate change that critics once may have thought him once “dotty” about.

In an interview Prince Harry conducted as guest editor for BBC Radio 4’s Today programme, he affectionately called his father “pa” and revealed how he has come to regularly “pick” his brains as he gets older.

As they explained their belief that humankind needs to work with and look after nature to save the planet, Prince Charles said: “Well my darling boy, it makes very proud to think that you understand.”

He added that it was “even more amazing” that his son had been listening to him for the many years he had been “banging on” about protecting the “viability of the planet”.

In a wide ranging interview on BBC’s flagship news programme, the father and son gave a tantalising insight into their close relationship as they revealed how they often talk for “hours and hours and hours” about environmental issues.