S1, E4: In the early 1970s, all was well in Windsor Castle. Queen Elizabeth II had balanced the demands of her extraordinary job and family, and capped the year with a lavish 25th wedding anniversary celebration. But over the next 20 years, bitter divisions and domestic disasters would rock the Royal Family, resulting in four doomed marriages and their 1,000-year-old home engulfed in flames. Witness the time when Windsor became home to one of the unhappiest families in Britain, as their secrets spilled out from behind the castle walls.