The suspect was tackled by officers after he emerged from the thousands of mourners lining Parliament Street by the Cenotaph on Monday and tried to leap over the metal gate holding crowds back.
It came as the late monarch’s coffin emerged from Westminster Abbey just before the full procession got underway, according to The Scottish Sun.
As the funeral procession moved past the Cabinet War Rooms, the Cenotaph and Downing Street, there was a hush from the crowd in Whitehall.
Some emerged from balconies and windows, clad in black, while those on the street craned their necks and clutched cameras as they awaited the chance to say goodbye to the monarch.
As it moved past the Cenotaph, the King, the Prince of Wales, the Princess Royal and the Earl of Wessex saluted the memorial to Britain and the Commonwealth soldiers killed in the First and Second World Wars.
After her State Funeral at Westminster Abbey, the late monarch’s coffin was borne on the State Gun Carriage, for a final journey pulled by Royal Navy ratings to Wellington Arch.
The procession, involving more than 3,000 members of the armed forces and on a scale of pageantry not seen since the funeral of King George VI in 1952, set off from the abbey at around 12.15pm.
More than 10,000 police officers were on duty for an unprecedented security operation for the first state funeral since the one held in 1965 for Winston Churchill, the first of 15 prime ministers during the Queen’s 70-year reign.
The Dean of Windsor will later conduct a private burial service attended by the King and members of the royal family at 7.30pm.
The Queen, who died on September 8 at the age of 96, will be buried at King George VI Memorial Chapel, and will rest alongside the Duke of Edinburgh.