A Royal guard fainted and fell off the podium where he was protecting the Queen's coffin, with police rushing to help him after he crashed to the ground.
Massive queues of mourners have been winding through the streets of London to see the Queen lying in state at Westminster Hall ahead of the funeral next Monday.
Soldiers marched with the coffin from Buckingham Palace on Wednesday but for one of the guards at Westminster Hall the strain appeared to be too much as he suddenly fainted.
There were gasps from mourners as he fell to the ground which was caught in a video.
It happened as a set of guards were beginning to swap duties and one appeared to be trembling before seconds later falling.
Two police officers could be seen racing over to pick him up before the video cut out and then went to images of the Houses of Parliament.
Shocked viewers also took to social media with one tweeting: "He must've been so overwhelmed with what was happening."
Another said: "Bless him - just happened to tune in; saw he was a bit wobbly and feared he'd faint. Hope he's ok."
Similar comments included: "Poor man, I hope he's alright. It was awful to see" and "It's such a massive responsibility during such a historical moment. I hope he's fine."
Earlier in the day, Lady Gabriella Windsor appeared to faint as the Queen's coffin arrived in Westminster Hall, reported Hello magazine.
Her husband, Thomas Kingston, could be seen helping as the coffin was brought in, while her mother, Princess Michael of Kent, looked on concerned.
Gabriella was not seen again after the incident while her parents both stayed for the rest of the service. She is known to have been close with the Queen, who attended her wedding in 2019.
And a Royal Archer collapsed as the Queen's coffin was carried out of St Giles' Cathedral in Edinburgh before it was flown down to London last Tuesday.
He and other Royal Archers had been standing outside the Cathedral waiting to march alongside the Queen's coffin when he started swaying and then fell to the ground.
Officials expect some 750,000 people will go to see the coffin with the line stretching several miles along the south bank of the River Thames, past landmarks such as Tower Bridge and a replica of Shakespeare's Globe Theatre, crossing Lambeth Bridge as it neared Westminster Hall.
