Three people have been taken to hospital after parts of the stands collapsed during a Trooping the Color rehearsal in central London.
A total of five people have been treated for injuries following the Horse Guards Road incident on Saturday morning, London Ambulance Service (LAS) said.
Dozens had turned up to watch the event, which is Major General’s review of the parade ahead of the full event on June 2 for the Queen’s Jubilee celebrations.
But just before 11 a.m. one of the stands gave way, leaving three injured, one of whom was taken to hospital.
A short time later, part of another grandstand collapsed and two other people were injured. One has been taken to hospital.
Emergency services assisted the injured and evacuated the grandstand before the parade was aborted and the entire area was evacuated.
An army spokesman said: “During the Major General’s discussion of the Horse Guards Parade, two sections of the lookout unfortunately failed, resulting in a small number of injuries.
“Emergency services were called to help the injured and the rest of the crowds were evacuated safely from the stands.
“Safety is our number one priority and we are urgently working with our partners and relevant organizations to understand what happened and make sure it doesn’t happen again.”
LAS said three patients were treated and discharged at the scene, but transport to hospital for one of the patients was arranged later in the day.
A spokesperson said: “We were called at 10:59am for reports of an incident on Horse Guards Road, SW1.
“We sent a tactical response unit, an ambulance crew, two bicycle rescuers and an incident response officer.
“We worked with volunteers from St John Ambulance to treat five people on site.
“We have taken one patient to a major trauma center as a matter of priority.
“St John Ambulance delivered a second priority patient to a major trauma center.
“We discharged three patients on the spot. We later arranged transport to the hospital for one of these patients.”
Alex O’Grady, 34, of Bromley, told the PA news agency that the incident was “surreal”, a “terrible condition” and that “people on the scene were in tears”.
He said: “We heard a big bang – at first we thought someone had fallen down a flight of stairs, turned around and saw a hole in the floor in the second row from the front of booth A.”
Mr O’Grady said he saw a woman yell across the hole at a man he believed to be her husband, but there was no response and paramedics soon began treating the man.
He added: “There was also a young child with a scraped knee, another man was clearly concerned and the woman was inconsolable.”
Another witness told the PA news agency: “There was a loud bang, then a scream and a voice yelling ‘help, help’.
“A number of ambulances were on the scene and stretchers were used for the victims.”
One Twitter user wrote: “It was a fun experience to watch until we got up for the national anthem, the grandstand next to us collapsed with someone falling through.”
“They aborted the procedure and the police started to evacuate us due to security concerns as there had already been two collapses for fear of more.
“It was certainly a very ‘British’ experience where we queued for an hour to watch horses and soldiers marching.”