People watched the state funeral and procession in London from big screens positioned along the road.
The largely black-clad crowd fell silent and the atmosphere grew sombre as the Last Post sounded and a two-minute silence followed.
Many then began to sing the national anthem when it played from the speakers afterwards.
The lyrics “God save our gracious King” rang out across Windsor while people bowed their heads and wiped tears from their eyes.
Later, marching bands proceeded from the castle down the Long Walk to Shaw Farm Gate, followed by cheers and applause from the crowds.
Elsewhere, hundreds of colourful bouquets brightened the base of Windsor Castle ahead of the procession of the Queen’s coffin through the Berkshire town.
Several mourners prayed and quietly shed a tear as they laid flowers for the Queen.
Jennifer Bryant said she wanted to come to the Long Walk in Windsor to say goodbye to the Queen, as the last time she had seen her in person was there 42 years ago.
Ms Bryant, 73, from Reading, recalled the “amazing experience” of seeing the Queen leaving for Royal Ascot in 1980, and how the Queen had waved to her and her three-year-old daughter.
She said that she felt emotional as the thousands of mourners in Windsor went quiet for the two-minute silence.
Ms Bryant added that for her, the Queen represented “stability and reliability” and she felt she had “kept our country stable” by always being there.
Anne Cooper described the atmosphere at the Long Walk in Windsor as “calm” as thousands came together to pay their respects.
Ms Cooper, from Aylesbury, Buckinghamshire, was draped in a Union flag as she watched the funeral on the big screens.
“She’s been the Queen all my life. I was a Brownie and a Guide so we would make a promise to serve the Queen, so she’s just a really big part of the country,” she said.
Gideon Rutherford said he wanted to take his three children to Windsor to be a part of this historic day, as he feels they will “remember it for the rest of their lives”.
Speaking from the Long Walk, Mr Rutherford, from Hampshire, said: “It’ll be a long time before we experience anything like this again in our lives, so it’s a moment in our country’s history and it’s important to experience it.”
His children, Edward, 11, and nine-year-old twins Theadora and Honor, attend Cheam preparatory school in Headley, Hampshire, where the King and his late father the Duke of Edinburgh studied.
Theadora and Honor said it felt “very special” to attend the same school as the King and they felt it was “very important” to be at Windsor for the Queen’s funeral as she “did a lot for our country”.
Artist Charles Minty, 41, from near Bath, said he arrived on the Long Walk in Windsor on Sunday, got a spot at the front by the barriers and had been painting ever since.
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Mr Minty, who was named after the King, having being born on the wedding day of the then Prince of Wales and Lady Diana Spencer, had finished a portrait of the Queen and had started working on a painting of Windsor Castle from the perspective of the crowds.
Speaking to the PA news agency, he said: “I finish the portrait as it is a tribute to the Queen and wanted to express how I feel through my art.
“I enjoy the energy I get from people who watch me paint, so as such a big event it is a way I can use my talent to express gratitude to Her Majesty.”
He added: “I’ve felt very emotional this morning. I was in tears, it was so moving, the atmosphere, the beautiful music playing.”
He added that he is “super tired” after having no sleep for two days.