A royal guard has suddenly collapsed while holding a vigil next to the Queen's coffin, stunning mourners shuffling into Westminster Hall to pay their respects.
Shocking footage from the 24-hour vigil shows the solemn guard swaying as he stands in front of the Monarch's coffin at around 12.30am on Thursday (local time).
He appears to loose his footing several times and briefly stepped off the podium, known as a catafalque, before gathering himself as the Gentlemen at Arms — the most senior of the sovereigns guards — file in and approach the coffin.
But just seconds later, the guard — wearing all black — faints, falling face first onto the ground as others rush to help.
Local publications report that the livestream of the vigil was cut for several minutes as police tended to the man.
Numerous viewers have posted the footage of the man collapsing online, wishing him a speedy recovery.
"Poor man, I hope he's ok. Probably heat and exhaustion," one woman wrote on TikTok.
"Hope he’s alright. He showed devotion and determination. He must be tired but he still tried to carry on," a man commented.
"Watching all these guards day after day, they must be exhausted and find it tough standing still for hours," another person said.
"You could see he was about to go, he should not have been allowed to collapse like that onto a dangerous stone floor," a fourth person criticised.
Three ceremonial units will guard the Queen's coffin as she lies in state before her funeral on Monday.
They are the Gentlemen at Arms, the Royal Company of Archers and the Yeomen of the Guard, according to Britain's ITV News.
It's understood the continuous 24-hour vigil is broken into four six-hour shifts, with the guards switching places every 20 minutes.
The guard isn't the only one who succumbed to exhaustion.
Two mourners waiting to enter Westminster Hall were treated by paramedics after collapsing in the heat, The Guardian reported.
Thousands pay respects at Queen's coffin
Mourners from all walks of life have filed past the coffin of Queen Elizabeth II through the night, paying their final respects to Britain's longest-reigning monarch.
After days of processions and ritual while the Queen's body was brought to London from Balmoral, Scotland, this was the opportunity for ordinary people to take a direct part in a ceremony.
Many were in tears as they passed by the flag-draped coffin.
Officials expect some 750,000 people to view it before the lying in state ends at 6.30am (3.30pm AEST) on Monday.
The line stretched back several kilometres along the south bank of the River Thames, past landmarks such as Tower Bridge and crossing Lambeth Bridge as it neared Westminster Hall.
Thomas Hughes, 20, who waited nearly 14 hours overnight with his brother, said finally viewing the coffin was quite overwhelming.
"You do it all because you want to pay respect to this lady ... and when you put yourself through that, and then you get to the moment you're waiting for, you are just that little bit more emotional," he said.
"It's a very powerful thing."
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