The Crown Jewels worn by Queen Elizabeth II may be sparkling and beautiful, but as she says in this clip from the Smithsonian Channel’s upcoming documentary, The Coronation, in which she makes a rare candid speaking appearance, they have some “disadvantages.”

“There are some disadvantages to the crowns, but otherwise, they’re quite important things,” the 91-year-old, record-breaking royal says of the item she wore only once, at age 25 on her coronation day nearly 65 years ago.

The Crown Jewels is part of the Royal Collection, which consists of 140 items and contains 23,000 precious stones. The headgear, known as St. Edward’s Crown, was destroyed after the English Civil War and remade for the Coronation of Charles II in 1661. It weighs nearly 5 pounds.

The one-hour TV special, which airs on Jan. 14, traces its history and sees Her Majesty looking back and sharing memories of that fateful day on June 2, 1952, as well as the coronation ceremony of her father King George VI in 1937.

As for the Coronation coach, Queen Elizabeth described the journey as “horrible.” “It’s only sprung on leather,” she explains. “Not very comfortable.”

“I’ve seen one coronation, and been the recipient in the other, which is pretty remarkable,” she later notes. “It’s the sort of beginning of one’s life, really, as a sovereign.”

The Coronation airs in the U.S. on Jan. 14 at 8 p.m. on Smithsonian Channel and was made in partnership with the BBC and Australian Broadcasting Corporation.