With the State Opening of Parliament looming Wednesday, the Queen will get "reacquainted" with the heavy Imperial State Crown, a palace insider tells PEOPLE
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Uneasy lies the head that wears a crown, Shakespeare famously wrote – especially when it weighs 3 lbs.!

Queen Elizabeth has been on the throne for more than 63 years and will break the record for the longest-reigning British monarch in September, but she still needs to practice wearing one of her heaviest pieces of royal hardware.

The Queen, 89, is preparing to wear her Imperial State Crown for one of her landmark ceremonial duties when she leads the State Opening of Parliament in London on Wednesday, following the general election held in the U.K. on May 7.

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She will have a couple of practice runs wearing the historic 3-lb. crown so that she can get reaccustomed to it, a palace insider tells PEOPLE. The crown is set to be transported under high security from its usual place of safekeeping at the Tower of London to Buckingham Palace before the ceremony.

“She will wear the crown in private at the palace to get reacquainted with it,” the source says.

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The crown features the famed “Cullinan Diamond,” which is the largest gem-quality diamond ever found, at more than 3,000 carats.

Says the Queen’s biographer, Robert Lacey: “Servants have spotted her wearing the Imperial State Crown while reading her papers from her red boxes the night before a State Opening to get used to her posture and the weight.”