Trooping the Colour, also known as the Queen's Birthday Parade, is an annual military parade to mark the reigning monarch's official birthday.
It is held in early June on the parade ground the other side of St. James' Park to Buckingham Palace, known as Horse Guards Parade.
Over 1,400 soldiers take part in the parade, more than 200 of them mounted on horses. Ten military bands, made up of roughly 400 musicians, perform the marching tunes. The Officer in Command of the Parade shouts some 113 words of command.
It is British military pageantry at its best.
The origin of Trooping the Colour
Trooping the Colour is now all about the pomp and pageantry, but it is based on an old military practice.
(MORE: Trump gets the royal treatment with state visit to the United Kingdom)The Colour is a term for the flag used to mark a regiment's position in the battle field. Each regiment would congregate around its Colour and young officers would march in between the ranks holding these flags high so that soldiers would know where to position themselves or come to if they had been separated from their regiment.
This practice was known as Trooping the Colour.
Who takes part in the parade?
As sovereign, Queen Elizabeth II is head of the British Armed Forces, and during Trooping the Colour, she will be greeted by a royal salute from soldiers of the Household Division; she will also inspect her troops. The queen used to inspect the troops on horseback, but now rides in a carriage.
The Household Division is responsible for guarding the monarch and performing on ceremonial occasions; its soldiers are also among the elite of the army's fighting force.
There are seven regiments in the Household Division: The Life Guards, The Blues and Royals, The Grenadier Guards, the Coldstream Guards, the Scots Guards, the Irish Guards and the Welsh Guards.
(MORE: Grandma goals: A look at Queen Elizabeth II with her grandkids and great-grandchildren)The reigning monarch is traditionally the Colonel-in-Chief of all the regiments of the Household Division.
There are currently four other Royal Colonels in the Household Division.
The Princess Royal is Colonel of the Blues and Royals, The Duke of York is Colonel of the Grenadier Guards, The Duke of Kent is Colonel of the Scots Guards, the Duke of Cambridge is Colonel of the Irish Guards and the Prince of Wales is Colonel of the Welsh Guards
What happens during the parade?
The royal carriage procession leaves Buckingham Palace with members of the royal family waving to the crowds that are lining the way from the palace down The Mall to the Horse Guard's Parade.
The queen travels in the Ascot Landau; since the Duke of Edinburgh has retired from public duty, she is expected to ride alone.
On arrival at Horse Guards Parade, the royal party goes to a viewing position on a balcony overlooking the parade ground while the queen, having inspected the troops, watches from a special platform or dais on the parade ground as the soldiers parade past.
The four royal Colonels of the Household Division will ride on horseback to the parade.
(MORE: Queen Elizabeth II celebrates 65th anniversary of her coronation: Look back at her royally good style)After the parade the royal party returns along the Mall in their carriages. The queen will then take a final salute before joining the rest of the royal family on the balcony at Buckingham Palace for the Royal Air Force fly past to mark her birthday.
This year, we expect to see all three of the Cambridge children – Prince George, Princess Charlotte and Prince Louis -- on the balcony. It is also hoped that the Duchess of Sussex will make an appearance, her first public one since she introduced her son Archie to the world on May 8.
This will be the queen's 67th birthday parade.