'It may still happen but there is no guarantee that we will see the Queen on the balcony during the birth anniversary.'
The presence of British Queen Elizabeth's Jubilee on the balcony of the palace among other members of the royal family is 'in no way guaranteed.'
According to a report in Daily Mail, the aides are busy preparing a "plan B".
"It may still happen but there is no guarantee that we will see the Queen on the balcony during the jubilee," the report quoted a reputable source as saying.
This is due to the Queen's mobility issue, the insider told the Mail.
However, there is still an expectation that the monarch will appear on the balcony at Buckingham Palace to mark the conclusion of his Platinum Jubilee.
The Duke of Sussex Prince Harry has also hinted that he may return to the UK with Meghan Markle and their children Archie and Lillibet for the ceremony.