The Royal Family will be out in force on Saturday 8 June 2019 for the annual Trooping the Colour ceremony.
It has marked the official birthday of the British Sovereign for over 260 years.
While the Queen actually turned 93 on April 21, official celebrations have often been held on another day, particularly when the actual birthday has not been in the summer.
Her Majesty’s great grandfather King Edward VII, for example, was born on 9 November 1841, but his official birthday was always marked in May or June when there was a greater likelihood of good weather for the Trooping the Colour parade.
The tradition is believed to date back to 1748, during King George II’s reign.
What happens at Trooping the Colour?
The Household Division’s website explains: “Regimental flags of the British Army were historically described as ‘Colours’ because they displayed the uniform Colours and insignia worn by the soldiers of different units.
“If Troops were to know what their Regiment’s Colours looked like, it was necessary to display them regularly.
“The way in which this was done was for young officers to march in between the ranks of troops formed up in lines with the Colours held high.
“This is the origin of the word ‘trooping’.”
On Saturday, over 1400 parading soldiers, almost 300 horses and 400 musicians will take part in the event.
The parade will start at Buckingham Palace and progress down The Mall to Horse Guard's Parade. Members of the Royal Family will travel alongside the parade on horseback and in carriages.
The Queen used to attend on horseback herself, but in recent years has travelled by carriage. She last rode on horseback in 1986.
Once the Queen has arrived at Horse Guard's Parade, Her Majesty is greeted by a royal salute and carries out an inspection of the troops.
The display closes with an RAF fly-past, watched by members of the Royal Family from the Buckingham Palace balcony.
Who will be attending?
The Queen is usually joined by members of the Royal Family during the parade and later on the balcony to watch the RAF fly-past.
The Prince of Wales, Duchess of Cornwall, the Duke and Duchess of Cambridge and their children are all expected to be among the attendees. Prince Louis may be making his balcony debut this weekend, as his older sister Princess Charlotte was one when she first attended.
The Duchess of Sussex is also expected to be making her first public appearance since the birth of her son Archie Harrison Mountbatten-Windsor.
The Queen’s large extended family will also join the family on the balcony.
How to watch
Members of the public can watch the parade from The Mall or on the edge of St James's Park overlooking Horse Guards.
The ceremony will also be broadcast live on BBC One from 10:30am in the UK.
Tickets for seats around the Horse Guards Parade are already sold out for 2019, as they are allocated by ballot.
If you want to attend in 2020, applications for Trooping the Colour are to be made between January and February only, via the Army website. Up to a maximum of four tickets can be applied.