Crisis consultant Mark Borkowski said he would advise the Sussexes to postpone the broadcast.
Public relations and crisis consultant Mark Borkowski warned that Harry and Meghan are at risk of a “real reputational mess” if they go ahead with the broadcast in the US on Sunday.
Harry’s grandfather Philip, 99, spent nearly two weeks in the private King Edward VII’s Hospital before being transferred to St Bartholomew’s Hospital on Monday for tests on a pre-existing heart condition.
Questions have been raised about the appropriateness of Harry and Meghan’s interview, which chat show queen Winfrey has promised will be “shocking” with “nothing off limits”.
Mr Borkowski told the PA news agency: “The timing is just horrendous.
“Anybody who looks at this through the optics of a caring family, even a family who are estranged from one another, it’s very uncomfortable as you edge towards Sunday.”
ITV has reportedly won the bidding war to screen the interview in a deal said to be worth around £1 million, according to MailOnline.
The CBS two-hour special will air on Sunday in the US and is expected to be shown in the UK on Monday March 8.
Mr Borkowski added: “This could be a real reputational mess for everybody involved.
“Harry and Meghan are supposed to be a sensitive, caring and empathetic brand.
“Surely the disruption, particularly to the Queen… but they’re going ahead with this juggernaut.”
If Philip’s health were to worsen, Mr Borkowski said Harry and Meghan’s fate would be “in the lap of the gods”.
“If you were strategically giving advice about mitigating reputational damage, you would show huge empathy by postponing,” he said.
Mr Borkowski said a deterioration in Philip’s health would also raise serious issues for ITV as to whether the screening should go ahead in the UK, and could cause problems for advertisers airing commercials during the programme.
“I think brands have to take a considered view about whether they want their advertising anywhere near this,” he said.
The royal household will be braced for the show’s revelations as the Sussexes discuss their life within the royal family and their exit from the working monarchy.
In dramatic promo clips, Winfrey asks Meghan if she was “silent or silenced”, with the duchess’s answer not revealed.
In response to a comment by the duchess, Winfrey asks: “Almost unsurvivable. Sounds like there was a breaking point?”
Harry is seen saying of his mother, Diana, Princess of Wales, while holding Meghan’s hand: “I’m just really relieved and happy to be sitting here, talking to you, with my wife by my side, because I can’t begin to imagine what it must have been like for her (Diana), going through this process by herself, all those years ago.”
At one point in the trailer, Winfrey tells viewers: “Just to make it clear to everybody, there is no subject that is off-limits,” as Meghan nods in agreement.
ITV has yet to comment.