This novel based on facts, brought back memories and sent me hunting on Google Images. Did Lady Diana Spencer really look so young and dress so badly before she became THE PRINCESS by marrying Prince Charles? The photos of her as a 20-year-old nanny in Kensington streets, suggest that yes, she really, really did.

The title is something of a misnomer, as we don’t see much of Diana’s Royal years. As a daughter of Viscount Althorp – who became Earl when his father died - and his wife Frances, who divorced, Diana was sent to boarding school with other girls of her class. She wasn’t a great scholar. The novel carries the tale by imagining a young, nervous schoolgirl in Diana’s year, Sandy, orphaned and out of place on a scholarship. Diana promptly stops others bullying Sandy and invites her home for half-term holidays, which gets us a look inside her stately home and family dynamics. Her father wanders in a dressing gown and slippers, her brother watches TV and chats, and her new stepmother frowns and criticises. Diana was devoted to traditional romantic novels at the age of thirteen, where many other girls would be reading novels of horses, mystery and fantasy.

We catch up with Diana later in life, when she invites Sandy, who hasn’t met her in years, to her rooms at Buckingham Palace. Now we learn how Diana met the Prince of Wales. Aged 30, Charles was given orders to marry for the future of the throne. Aged eighteen, Diana knew her older sister Sarah had dated Charles but been considered unsuitable. The story explores why Sarah, and all of Charles’s other girlfriends, were unsuitable and why there were no princesses from European royalty he could marry.

Wendy Holden has been a journalist in newspapers and magazines, and she shows the point of view of some dedicated royal-watchers, whose front-page snaps sold thousands or millions of copies, who had to fit puzzle pieces together as they worked out who might be the royal bride – while wishing her all the best. She also researched memoirs written by former palace staff, so we see who did what in bleak, impersonal edifices. Diana asks questions which I was sure she’d know the answer to, as a way to explain to the reader. Some comedy is present, but also dry wit and plenty of sorrow, as we foreshadow events. Diana, we are shown here, always wanted a fairytale marriage that would be more loving than her parents’ – but that was not to be. THE PRINCESS kept me engaged and reading and, as I say, looking back at the photos. This splendid, big-hearted book is the third in a series called Royal Outsiders.