The Queen’s husband, 99, was admitted to hospital on Tuesday night local time as a “precautionary measure” after feeling unwell, the palace confirmed.
Now, The Mirror reports the Duke of Sussex is in self-isolation at his home in Montecito, California so he can fly back to England at short notice if Philip’s condition worsens.
Harry has already made arrangements to fly home via private jet, reports royal editor Russell Myers, and is being regularly updated on his grandfather’s condition.
Speaking to Today, Myers said he felt the measure was “the right thing to do” for the duke.
“He’s stuck in California, the US has increasing COVID rates at the moment and Prince Harry wants to be able to jump on a plane at a moment’s notice,” he said.
“I’m told things are in place already for him to make that move if he needs to, if indeed Prince Philip takes a turn for the worse.”
Prince Philip is expected to remain in London’s King Edward VII Hospital hospital for several days under observation.
Myers said Harry has been staying at home with wife Meghan Markle, who is currently pregnant with the couple’s second child, and their son Archie.
Harry would be tested for coronavirus before leaving the US and before entering the UK, Myers reports.
It’s not known whether Meghan would accompany her husband on the trip; the duchess is believed to be about five months into her pregnancy.
The Mirror’s report has not been confirmed or commented on by the Duke and Duchess of Sussex.
If Harry does end up returning to the UK, it would be his first trip home since he and Meghan resigned as senior working royals and moved to the US in 2020.
There had been speculation the prince would return for the the unveiling of a statue of his late mother Princess Diana at Kensington Palace in July.
Myers told Today the palace did not intend to give “rolling updates” on Prince Philip’s condition, having already confirmed he would spend several days in hospital.
“He is in good spirits, we are told, he walked into hospital unaided … the ‘iron duke’ has not been one to put up a fuss,” he said.
“He had been ill for several days but, typically, didn’t want a fuss being made about him and had to be persuaded to go to the hospital by the royal doctors.”
In four months time, the Duke of Edinburgh will turn 100.