The fourth episode of the gripping saga of the world's most famous dynasty features intimate letters from the Prince of Wales and previously unseen family photos of the aristocratic relative earmarked by Charles' great uncle for him to marry in the late 1970s. Charles was determined to do the right thing as Prince of Wales and avoid the mistakes of his great uncle King Edward VIII, who abdicated to marry the divorced woman who he loved, and almost brought the House of Windsor to its knees. Another great uncle, Lord Mountbatten - an ambitious man of boundless energy and ego - wants to cement his position at the heart of the House of Windsor by acting as kingmaker to Prince Charles, who calls him his 'honorary grandpa'. The programme reveals how Mountbatten arranged a secret meeting in Paris between the exiled King and Charles. But, rather than fearing 'Uncle David' as a warning from history, Charles describes how he sees him as an object of sympathy, even affection.As Prince Charles comes of age, he faces pressure to avoid the romantic pitfalls of Edward VIII, and is taken under Lord Mountbatten's wing.