'Fondest love, Pa': That's how Prince Philip signed all his letters to Diana as - with typical bluntness, but surprising warmth - he tried to save her marriage to Charles. RICHARD KAY reveals the most intriguing royal friendship of all Prince Philip was a decisive and worldly man whose frankness Princess Diana admired, the only man in the House of Windsor, she felt, who listened to her Philip was the figure within the family who was on familiar terms with real world Princess Diana had come to know Philip as someone who was understanding