Three military personnel had to be assisted by colleagues after appearing to get into difficulty by Wellington Arch shortly before 2pm.
One appeared to collapse to the ground after the Royal Family had left, while two others were also seen being helped away before and after the transfer of the Queen’s coffin to the state hearse by the monument.
At Hyde Park Barracks another member of military personnel stumbled and was taken away by a colleague.
Earlier in the day, a police officer on duty just off Parliament Square was photographed being carried away on a stretcher by Naval personnel after collapsing.
Officers from the Metropolitan Police and a number of outside forces that have sent officers to help have had all leave cancelled and many have been working shifts of 12 hours or longer since the Queen’s death.
St John Ambulance gave support to hundreds of members of the public who joined the crowds to say goodbye to the Queen.
It said that between 8am and 1pm on Monday it had treated 238 patients, of whom 36 had been taken to hospital.