Queen Elizabeth's reign is "effectively over" as a result of the Covid-19 pandemic, as one royal biographer claimed it's "practically put Charles on the throne".
Andrew Morton, the author of Diana, Her True Story, said coronavirus had damaged the monarchy "more than Oliver Cromwell", according to the Daily Mail.
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The Queen, 94, reportedly may remain in self-isolation for months and never return to her usual royal duties as the UK lockdown eases over the coming weeks.
Her Majesty has put all her public engagements on hold while living with her husband Prince Philip at Windsor Castle.
Morton told Britain's Daily Telegraph it was "terribly sad" but he couldn't see the Queen resuming her job.
"The Covid-19 virus isn't going away soon and will be with us for months if not years," he said.
"[It would be] far too risky for the Queen to start meeting people on a regular basis."
The Queen loves getting out and about and meeting people but the risk is too great, he said.
"The brutal truth is that her reign is effectively over. Covid-19 has done more damage to the monarchy than Oliver Cromwell. Corona has practically put Charles on the throne."
Morton previously told The Sun he feared the Queen may never be able to return to her usual duties and will likely be seen on video links or TV rather than in public.
Last month a Buckingham Palace spokesperson said the Queen was keeping busy with a weekly audience with the UK Prime Minister over the phone and getting her daily red boxes of government papers.
Buckingham Palace will be closed over summer for what is reportedly the first time in 27 years, as event such as Trooping the Colour and the Queen's garden parties are cancelled.
It's believed to be her longest absence from official duties in her 68-year reign.
Her last public appearance was at the Commonwealth Day service in March at Westminster Abbey, also Harry and Meghan's last official appearance as members of the royal family.
A source told the Sunday Times that the Queen would not do anything that goes against the advice for people in her age group.
"She's going to take all the appropriate advice ... she'd want to be seen to be being responsible in her actions."