Queen wishes to make the most out of Platinum Jubilee as she misses events leading up to the celebrations.
Tuesday marks the third time the 96-year-old opted out of the State Opening of Parliament in 70 years and royal experts believe it is time for her to pass on the Crown to son Charles.
However, royal commentator Richard Fitzwilliams tells Express.co.uk: "The Opening of Parliament is symbolically a highly significant occasion that the Queen has not missed in nearly 60 years.
"Since she has not attended many public events since October and considering the physicality involved in this, as she is suffering from 'episodic mobility problems' her absence is not surprising."
He continued: "The Queen is obviously intending to be present as much as possible during her Jubilee celebrations.
"She is also active virtually and recently received the President of Switzerland without needing her walking stick.
"Obviously today is highly significant for Charles but it can also be seen as part of the gradual takeover of the Queen’s duties, such as laying the wreath at the Cenotaph on Remembrance Sunday, that was gradually happening anyway."
Meanwhile, Prince of Wales, Charles, is stepping in place of his mother.
He said: "It is important to stress that the Throne, symbolic of her authority, will remain vacant."
For the event, Charles will wear his Admiral of the Fleet uniform.
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"The Horse Whisperer", published in 1995, was Evans´ debut novel and earned him widespread global acclaim.