Members of the rapidly-gathering crowd laid flowers outside the royal residence, where the Queen spent much of lockdown, and sobbed openly as the Union Flag was lowered to half mast.

Within minutes, the throng of mourners had grown so dense that members of staff returning to the castle were struggling to reach the entrance.

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One woman, who gave her name as Lisa and was visiting from Florida, said the impromptu gathering felt “special” because everyone was united in grief.

“I’m surprised at all the different kinds of people that are here,” she said.

“I’m hearing lots of different accents, lots of different cultures are represented, it’s a very nice thing.

“The world being as it is today, this is something we all agree on.

“The Queen is just somebody I’ve always admired.

“I think her character is just beyond reproach… she’s lived a really good life.”

Her eyes filling with tears, Lisa gestured to the rainbow and added: “It’s fading a little bit but it’s been beautiful.”

Well into the evening, crowds were streaming up from shops on nearby Peascod Street, their arms laden with floral tributes for the Queen.

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Roses, tulips, elderflower and even potted plant were laid outside the Castle as people paid their respects with whatever they could lay their hands on.

When it had grown dark and the police had ushered the mourners back, they decorated a nearby statue of Queen Victoria with more flowers and candles.

Denise Speck brought a bouquet of roses from the local Marks & Spencer, which was due to close at 7pm but stayed open late for well-wishers.

Ms Speck, on holiday from Perth, Australia, had intended to visit Windsor on Friday but moved her trip forward a day after hearing the Queen was unwell.

“I just feel very blessed to be here at this time… my family back in Australia won’t even know yet because it’s the middle of the night,” she said.

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Saying that the world had entered a “new era” without the Queen, Ms Speck speculated that Australia and other Commonwealth countries could start to grow apart from Britain.

She said: “The Queen was something that everyone admired even though they didn’t necessarily want to be part of the British system.

“It’s the Queen that was the glue that kept it all going.”