Ms Truss opened up about her last encounter with Queen Elizabeth II in Balmoral Castle just two days before the monarch died.
Speaking to GB News to mark the first anniversary of the late Queen’s death and recounting the period that followed, Ms Truss recalled the King was “very, very resolute” when she spoke to him on the phone the day his mother died and his reign began.
The late Queen had welcomed Ms Truss to her home in the Scottish Highlands on September 6 2022 to appoint her prime minister, with health issues meaning she was not able to travel to London to do so.
The politician described the 96-year-old sovereign as appearing “frail”, but she said she was “mentally alert”, “absolutely on top of” the proceedings and reassured Ms Truss they would meet again soon.
Ms Truss said: “In the meeting at Balmoral, she was absolutely on top of what was happening.
“She was very, very keen to reassure me that we’d be meeting again soon. It was very important to her.”
She added: “Although she was physically quite frail, she was absolutely mentally alert.”
Ms Truss said there was no indication the late Queen was gravely ill.
“I was obviously only in the first few days of the job of being prime minister. I was thinking about many, many different things,” she said.
“But the assumption absolutely was that this would be the first of many meetings.”
The monarch, using a walking stick, was pictured smiling warmly as she greeted Ms Truss in front of an open fire in her sitting room at the castle, appearing frail but bright-eyed and wearing a blouse, cardigan, and a skirt of Balmoral tartan.
Ms Truss added: “She was very determined to do her duty, right to the end. We had a very, very good meeting. She was upbeat.”
The former prime minister recounted how she was told of a worsening situation on September 7 – with the postponement of a Privy Council.
“I arrived just before 6pm for the meeting. Everybody was there waiting around and we waited for a few minutes and then the news arrived that the Queen would no longer be able to do the meeting. And that was the first I heard of it. But clearly it was a very ominous sign,” she told GB News’ royal correspondent Cameron Walker.
She said of September 8: “Things were clearly getting even worse the next day, so it was a dawning realisation I think, not just for me, but for my colleagues, that we were facing (it).”
Ms Truss was in the House of Commons chamber for an energy debate at around midday that day when the then-chancellor of the Duchy of Lancaster Nadhim Zahawi sat down next to her with a note and began urgently whispering to her.
The original plan was for Buckingham Palace to release a statement about the late Queen’s health at 11.15am, but it was delayed.
Mr Zahawi’s note contained a statement for Ms Truss to read out to the Commons if required.
In the end, Ms Truss left the chamber and headed back to Downing Street, and the Palace’s statement saying Queen Elizabeth II was under medical supervision was issued at 12.32pm.
Ms Truss said she was really just waiting for the news and by that point knew it was “very, very serious”.
Describing the scene in Number 10 when confirmation of the late Queen’s death reached them at around 4.30pm, she said: “We were in the Downing Street flat with officials, other people. So when the news came through, it was sort of confirming all the worst fears that we’d had.”
Ms Truss said she felt very sad about the situation, but her mind also turned to the practicalities of the days to come.
“Just knowing that I would have to deal with it. You know, part of your brain is thinking, my goodness me, this is a momentous occasion. This is our Queen who’s been on the throne for 70 years, the absolute backdrop to our lives is now gone,” she said.
“But also, I tend to focus on the practical in those types of moments and just thinking right, I need to make sure my speech is ready. I need to make sure the right people are informed. I needed to make sure that the Cabinet ministers responsible for organising (were ready for) what was going to be a massive international occasion.”
A pre-arranged statement for a sitting prime minister to read in the event of the monarch’s death had long been drafted, but was reportedly out of date in tone so Ms Truss rewrote it.
“I wanted to say it in my own words so I drafted it with a speech writer,” she said.
She spoke to the King the same day and offered her “sincere condolences” and said that during the brief phone call he was “very, very resolute”.
She added of the new monarch: “King Charles is somebody who’d also been a very prominent part of British life. I think we’ve seen the continuity …
“I think because both of us were stepping into new roles, a lot of what you’re thinking about is the practicalities of getting things done.”
When the King held his first weekly audience with Ms Truss on October 12, he welcomed her to the Palace by saying: “Back again? Dear oh dear.”
Mr Truss insisted it was a joke and said the pair were at their third meeting that day.
She paid tribute to the late monarch as a major figure for Britain who was “still very, very, very loved and treasured”.
“And she was still very much with us until the end, absolutely,” she said.
“And that’s what just struck me about her is that right until that moment, she wanted to be there doing her duty.”
The best videos delivered daily
Watch the stories that matter, right from your inbox