“On the death of her father King George VI, Winston Churchill said the news had stilled the clatter and traffic of 20th-century life in many lands,” she said.
“Now, 70 years later, in the tumult of the 21st century, life has paused again. Her late Majesty Queen Elizabeth II was one of the greatest leaders the world has ever known.”
Earlier, MPs, dressed in dark clothing, had bowed their heads to observe a minute’s silence to mark the death of the nation’s longest-reigning monarch.
Opening two days of special tributes in Parliament, Ms Truss said the new King “bears an awesome responsibility that he now carries for all of us”.
"In an instant yesterday, our lives changed forever,” she told the hushed chamber. “Today, we show the world that we do not fear what lies ahead.”
The Queen was, Ms Truss said, “the nation’s greatest diplomat”, embodying “the spirit of our great country”.
She concluded: "The crown endures, our nation endures, and in that spirit I say God save the King.”
Amid the sadness, there was laughter, too.
In a moving speech, Boris Johnson, who just a few days ago still held the keys to Downing Street, recalled a conversation with the Queen during the London Olympics.
Famously, the opening ceremony had included a filmed section in which Elizabeth appeared to parachute into the stadium with James Bond.
Mr Johnson told MPs: “I remember her innocent joy more than ten years ago, after the opening ceremony of the London Olympics, when I told her that the leader of a friendly Middle Eastern country seemed actually to believe that she had jumped out of a helicopter in a pink dress and parachuted into the stadium.”
Former prime minister Theresa May, who described the Queen as “quite simply, the most remarkable person I have ever met”, also sparked laughter with her memories of meeting the monarch.
She recalled a picnic at Balmoral in which everyone mucked in to lay out food and drink on a table.
"I picked up some cheese, put it on a plate and was transferring it to a table,” the former Conservative leader said. “The cheese fell on the floor. I had a split-second decision to make.
"I picked up the cheese, put it on the plate and put it on the table. I turned round to see that my every move had been watched very carefully by Her Majesty The Queen.
"I looked at her, she looked at me, and she just smiled – and the cheese remained on the table.”
Her audiences with the Queen, Mrs May said, were “not meetings with a high and mighty monarch, but a conversation with a woman of experience and knowledge and immense wisdom”.
She added: “They were also the one meeting I went to which I knew would not be briefed out to the media.”
Both Houses of Parliament sat on Friday and into the weekend to allow politicians to pay tribute to the Queen.
Labour leader Sir Keir Starmer hailed the Queen’s “total commitment to service and duty, a deep devotion to the country, the Commonwealth, and the people she loved”, adding: “In return for that, we loved her.
“And it is because of that great shared love that we grieve today. For the 70 glorious years of her reign, our Queen was at the heart of this nation’s life.
“She did not simply reign over us, she lived alongside us, she shared in our hopes and our fears, our joy and our pain. Our good times and our bad.”
He added: "When everything is spinning, a nation requires a still point. When times are difficult, it requires comfort, and when direction is hard to find, it requires leadership.
"The loss of our Queen robs this country of its stillest point, its greatest comfort, at precisely the time we need those things most."
SNP Westminster leader Ian Blackford paid tribute to the Queen as “one of the true constants in all our lives” and “a steady hand guiding the ship and the perpetual symbol of stability”.
He said: “She was a monarch who reigned with compassion and integrity and established a deep connection with the public.
“The affection which the Queen had for Scotland, and that Scotland had for the Queen, cannot be under-estimated.
“The relationship between Scotland and the Queen was one of shared admiration.
“Indeed, whilst she was everyone’s Queen, for many in Scotland, she was Elizabeth, Queen of Scots.”
Conservative former leader Sir Iain Duncan Smith was visibly emotional as he quoted from W H Auden’s famous poem Funeral Blues.
Earlier, Commons Speaker Sir Lindsay Hoyle hailed the Queen’s “magnificent service” and sent his “deepest sympathies” to the King and other members of the royal family.
He said: “Over her reign she has seen unprecedented social, cultural, technological change. Through it all she has been the most conscientious and dutiful of monarchs.
“But whilst she understood the unescapable nature of duty, which sometimes must have weighed upon her heavily, she also delighted in carrying it out for she was the most devoted monarch.”
He added: “Our memories of her will be filled with that image of a gently smiling dedication that showed throughout her life.”