A glimpse into the future as Charles reads Queen's Speech for the first time

The Queen's throne will be empty and Prince Charles will read the speech for the very first time

The Throne in the House of Lords will be empty on Tuesday.

It will be a visual reminder of the Queen's absence.

Prince Charles will take a seat next to where his mother would be - and he will instead read the speech written for the Monarch by her government.

On either side of him, there will be Prince William and the Duchess of Cornwall. Only twice before has the Queen missed this appointment in her diary - in 1959 and 1963.

The opening by the Sovereign of the new session of Parliament is a key moment in her role as Head of State.

But she has been forced to cancel with less than 24 hours notice due to her ongoing mobility issues.

It's not difficult to see why - the walk she has done many time before is a long one.

It involves moving from the Sovereign's Entrance of the Houses of Parliament, to the Robing Room, through the Royal Gallery and into the chamber of the House of Lords.

It is not something the Queen's doctors thought she should do.

And so this afternoon, the Queen issued Letters Patent which authorise her to delegate the Royal function of State Opening to Counsellors of State.

The most senior of which are the Prince of Wales and the Duke of Cambridge.

They will jointly exercise this function and Prince Charles will read the words on the Queen's behalf.

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The Duchess of Cornwall - the future Queen Consort - is not a Counsellor of State.

And it is a moment to ask what would happen if Charles or William were unavailable as the next two Counsellors of State are Prince Andrew and Prince Harry - both of whom are not longer working members of the Royal Family.

Prince Charles has never had to read the Queen's Speech before (in 1959 and 1963 it was the Lord Chancellor who read it for the Sovereign).

But he is now standing in for the Queen more and more: every year at Remembrance Sunday, very recently at the Commonwealth Day service and at the Royal Maundy, he travels abroad on her behalf.

But one day, Charles will occupy the throne which will sit empty on Tuesday and read the speech Monarch.

The State Opening of Parliament in 2022 will therefore be a glimpse into the future.