The 95-year-old recently stayed overnight in hospital for the first time in eight years
After cancelling a visit to Northern Ireland last week, the Queen was advised to rest and admitted to hospital for “preliminary investigations” during her first overnight stay at a medical facility in eight years.
She returned to Westminster on Thursday and was advised to rest for at least two weeks and undertake only “desk-based duties”, Buckingham Palace announced.
The 95-year-old on Friday recorded her speech for the Cop26 climate summit as she will no longer travel to Glasgow to take part in the UN conference.
She is, however, said to be in good spirits, according to the prime minister.
Speaking to ITV News in Rome, Mr Johnson said: “I spoke to Her Majesty as I do every week as part of my job and she was on very good form.
“She has been told by her doctors that she has got to rest and I think we have got to respect that and understand that and everybody wishes her all the very best.”
The Queen does intend to lead the country in honouring the country’s war dead on Remembrance Sunday.
She was recently seen using a walking stick at a Westminster Abbey service, the first time she has done so at a major event.
In a statement on Friday, the palace said: “Following on from their recent advice that the Queen should rest for a few days, Her Majesty’s doctors have advised that she should continue to rest for at least the next two weeks.
“The doctors have advised that Her Majesty can continue to undertake light, desk-based duties during this time, including some virtual audiences, but not to undertake any official visits.
“Her Majesty regrets that this means she will be unable to attend the Festival of Remembrance on Saturday, November 13.
“However, it remains The Queen’s firm intention to be present for the National Service of Remembrance on Remembrance Sunday, on November 14.”