As Pope Francis continues to fight double pneumonia in hospital, many have begun to wonder what the process would be if he were to step down on health grounds like his predecessor, Pope Benedict XVI.The method the Catholic Church uses to select their leader has remained virtually unchanged for the last 800 years.

The cast of award-winning movie 'Conclave' have sent their well wishes to Pope Francis after it was revealed the pontiff is in critical condition in hospital as he battles pneumonia and bronchitis.

Concerns over Pope Francis' health have mounted in recent years as have questions about his succession. Here's what we know.