Forty years ago on 1 July 1969, Wales celebrated one of the great royal events of the 20th century: the investiture of Prince Charles as Prince of Wales. A day of pomp and pageantry, but also a day of bombs and threats to the lives of the Royal Family. Huw Edwards recounts the events of an extraordinary day, when police, politicians and royalty held their breath as a few nationalist extremists violently plotted against the investiture.