The Queen has received an historic "Feu de Joie" rifle salute as part of her 80th birthday celebrations.
The crowd applauded the Queen and the Duke of Edinburgh.
The cascade of blank gunshots was common in the 18th and 19th centuries to mark a military victory or birthday.
But it was thought to be the first time it had been performed in the current Queen's presence during her reign.
Three cheers from the guardsmen followed. The Queen had earlier watched the Trooping the Colour parade and a spectacular 49-plane RAF flypast.
The RAF display, which departed from Suffolk, featured planes including modern Typhoon fighter jets, World War II aircraft and the Red Arrows.
More than 1,100 soldiers took part in the Trooping the Colour ceremony - wearing the traditional bearskin hats and scarlet tunics as temperatures soared to almost 30 C.
Afterwards, on the red gravel outside Buckingham Palace, a contingent of guardsmen removed their hats as they gave the Queen three cheers.
Joining in with the good wishes were tens of thousands of people had lined the Mall, in Central London, to catch a glimpse of the pomp and pageantry and then moved back in front of the palace.
Earlier they broke into applause as the Queen and the Duke of Edinburgh rode in Queen Victoria's 1842 phaeton carriage from Buckingham Palace along The Mall to Horse Guards Parade.
The Queen, wearing a mauve silk dress with a flower motif and a deep purple fine wool coat, inspected the troops before rejoining her husband on a dais to watch the ceremony which included a marching band.
Most of the royal family were in attendance at the celebrations including Prince Harry, who wore military uniform at the parade for the first time, having joined the Blues and Royals earlier this year after passing out from Sandhurst.
Prince Charles, the Princess Royal and the Duke of Kent all followed the Queen's carriage on horseback.
However Prince William, who is at Sandhurst, was not present and neither was the Duchess of Cornwall, who is in mourning for her father who died this week.
Marching and horsemanship
The Queen has two birthdays - her actual one on April 21 when she turned 80 - and her official one on a chosen weekend in June.
The historic Trooping ceremony is a spectacular display of precision formation marching and horsemanship choreographed to military band music.
It comes from traditional preparations for battle when colours or flags were carried or "trooped" down the ranks so that they could be recognised by the soldiers.
Only one colour is carried along the ranks each year and this time it was the turn of the 1st Battalion Welsh Guards.
Prince Harry sat in a carriage with his uncle, the Duke of York
Four of the five Foot Guards regiments of the Household Division - the Welsh Guards, Grenadier Guards, Scots Guards and the Coldstream Guards - were on parade.
The Massed Bands and the Mounted Bands of the Household Cavalry performed an array of rousing tunes.
The Queen has attended Trooping every year during her reign except 1955 when it was cancelled because of the general strike.
Ninety solders from the Coldstream Guards, Welsh Guards carried out the Feu de Joie.
They held their rifles aloft and fired three short, sharp bursts of gunfire - which were in fact blanks.
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