Royals Princess Diana and Prince Charles Chose William's Name to Set His Course as a Legendary King and Conqueror Royal historian Robert Lacey exclusively writes in this week's PEOPLE about inspirations behind their future king son's powerful names By Robert Lacey and Simon Perry Published on October 1, 2021 02:00 PM Share Tweet Pin Email Photo: Max Mumby/Indigo/Getty Royal historian Robert Lacey, author of the best-selling Battle of Brothers, exclusively writes this week's PEOPLE cover story, offering insights on the state of the monarchy, the Queen's legacy in action, and William and Kate's eye toward their future on the throne When Prince William ascends the throne, he will be known as King William IV — but the prince's name as a monarch could have been entirely different if Prince Charles had his way. Historian Robert Lacey writes exclusively for this week's PEOPLE that Charles had his heart set on another legendary king's name for his firstborn son: Arthur — but "Diana, Princess of Wales proposed a more robust name — William, as in 'William the Conqueror,' victor of the famed Battle of Hastings in 1066." And so it was settled. When he was born in June 1982, William took his first name would take from the warrior who was crowned King on Christmas Day. Jayne Fincher/Princess Diana Archive/Getty That first King William set about building "formidable stone castles — notably the fortress overlooking the River Thames at Windsor, from which Britain's modern royal family have taken their name and where the Queen now spends much of her time," writes Lacey, a veteran royal historian and author of the best-selling book Battle of the Brothers. Can't get enough of PEOPLE's Royals coverage? Sign up for our free Royals newsletter to get the latest updates on Kate Middleton, Meghan Markle and more! That said, Charles's preferred name of Arthur was not entirely rejected — Prince William's second name is taken from the legendary King of the Round Table. His grandfather, Prince Philip, inspired third name, and the name Louis rounds out the mix — a name he has since passed down to his second son when he and Kate Middleton welcomed Prince Louis (whose second name is also Arthur) in 2018. Shutterstock Bolstered by the legacies of these legendary men — not to mention the enduring, formative influence of his grandmother, Queen Elizabeth — William has a lot to look (and live up) to as he considers his impending reign. How Kate Middleton and Prince William Are Raising the Next Generation of Royals But according to Lacey, his mother knew from his earliest years he would live up to his profound name(s): "'He's obviously going to be a great King,' Diana would declare to her confidante Simone Simmons as she watched her son organize pickup games of soccer in Kensington Palace's gardens or subversive midnight feasts on sleepovers with friends. 'Look how they're drawn to him! He's a born leader.'"