Kate Middleton has never been invited aboard Queen Elizabeth's royal train in her 10 years as a member of the royal family. It's the one privilege she has yet to experience when her sister-in-law, Meghan Markle, had been inside the train in 2018.

According to Daily Express, the Queen's royal train is not the rest of family's most preferred mode of transportation since its rather a slow ride. They have cars, choppers, and private planes to get to their engagements, which are likely more on par with Kate's needs.

But Her Majesty likes taking this old transportation for her long travels across the country because she can relax in the suites and see the British countryside. The royal train has bedrooms, a spacious 12-seater dining room, a luxury smoking room, offices, and a tub in the Queen's suite. Royal historian David McClure said in the documentary Secrets of the Royal Train that the locomotive is not exactly for flamboyance but more for function.

Only four senior royals are usually privileged to ride this train around the United Kingdom: Queen Elizabeth, Prince Philip, the Duke of Edinburgh, Prince Charles, the Prince of Wales, and Camilla, the Duchess of Cornwall. Prince William may have been inside the royal train only once in his 38 years, but his brother, Prince Harry, has never been on it as well, just like Kate.

However, Meghan was able to ride the royal train with Queen Elizabeth because she happened to have a royal engagement in Cheshire, England, with Prince Harry's grandmother. Grant Harrold, the Queen's former butler, told CNBC that it made sense for the Duchess of Sussex to ride with the Queen since this was the mode of transportation Her Majesty chose for the trip.

Queen Consort Adelaide, the wife of King William IV, was the first royalty to use the train in 1840. However, Queen Victoria was the first monarch to ride the transportation two years later.

Admittedly, however, this locomotive has been quite outdated since the 1970s. But the royal train won't likely be decommissioned soon, unlike the royal yacht, the Britannia. Queen Elizabeth still insists that she needs the train to carry out her duties.

There are speculations that Kate and Prince William may likely ride the royal train together once Prince Charles in the monarch and inherits his mother's other privileges. Next to the Queen, the Prince of Wales apparently loves the train rides, but Camilla is not a fan of the locomotive in the same way that Prince Philip feels riding the royal train makes him feel like a poached egg.