LONDON -- Huge crowds in central London gathered on Thursday to honour Queen Elizabeth II's Platinum Jubilee, with a massive military salute kicking off festivities.

"It's a beautiful day in London. And this is a once-in-a-lifetime event. The only way to actually see it is to get here very early in the morning, which a lot of people did," said CTV National News Chief International Correspondent Paul Workman.

The military salute, known as the Trooping the Colour, is a tradition that dates back to the 18th century to celebrate the official birthday of the sovereign. It's a ceremonial re-enactment of the way battle flags were once shown to soldiers to make sure they would recognize a crucial rallying point if they became disoriented in combat.

"It goes back to 1755 when the first salute is given to the monarch. It's become something much more symbolic, much bigger since then -- a symbol of the endurance of the Royal Family, of the pageantry and the efficiency of the British military. And of course, a symbol of the Great Imperial British age," Workman said.

But the 96-year-old monarch has increasingly been delegating her duties to younger members of the family. For this year's Trooping the Colour, the Queen deputized her heir apparent, Prince Charles, to take the salute on her behalf, offering a "glimpse of what the future is going to look like when the Queen is gone," said Workman.

With files from The Associated Press.

Watch the full video with CTV National News Chief International Correspondent Paul Workman at the top of the article.