The Queen has reportedly left a ‘secret’ letter with strict instructions it is not to be opened until 63 years after her death.

Her late Majesty passed away peacefully last Thursday at the age of 96, sparking a period of national mourning which will end with the late monarch’s funeral on Monday.

Queen Elizabeth II will seemingly be sharing her wisdom long after her death after leaving a letter to citizens of Sydney with orders it cannot be opened until 2085.

The Queen was head of state of Australia and had previously written a letter that has been hidden in a time capsule in a building dedicated to Queen Victoria, her great-great grandmother.

After the restoration of the Queen Victoria Building in 1986, the late monarch left the mysterious letter to the Lord Mayor of Sydney.

Instructions on the letter read:  “On a suitable day to be selected by you in the year 2085AD, would you please open this envelope and convey to the citizens of Sydney my message to them,” according to News.com.au.

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The letter has been kept in a glass case in a restricted part of the building signed “Elizabeth”.

The contents of the letter are so secret not even the Queen’s personal staff know what is written.

Thousands of mourners continue to queue through the night to pay their respects to the late monarch.

People from all over the world have joined a mile-long queue for the chance to file past the monarch’s coffin after it was handed to the care of the nation on Wednesday afternoon.

By 8am on Thursday, the queue was around 2.6 miles long.

The coffin, which sits on a catafalque and is draped with a Royal Standard, continues to be guarded at all hours by units from the Sovereign’s Bodyguard, the Household Division or Yeoman Warders of the Tower of London.