The New Royals author Katie Nicholl says despite the Queen's absence from the thanksgiving service in her honour, there is "no need" for "alarm bells to be ringing".
"It is a shock, I know people tuning in this evening are thinking, 'oh gosh, this is not good'," Ms Nicholl told Sky News Australia host Piers Morgan.
She said, however, she was told by a "source close to the Royals" that "nothing was certain".
"The fact that we've had two balcony appearances today, the lighting of the beacons this evening, I think suggests there's no need for alarm bells to be ringing."
Despite this, she said it will "look very strange" for the Queen to be absent from the service.
