Prince William and his wife Catherine took part in the pomp and pageantry on Saturday as Queen Elizabeth II celebrated her official birthday.
William, her grandson, wore his wedding uniform - this time complete with a bearskin hat for the traditional Trooping the Colour military parade in central London.
Dressed in the scarlet tunic of the honorary colonel of the Irish Guards, the Duke of Cambridge rode on horseback as Catherine joined other royals watching from a window.
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It was the public's first chance to see the royal family all together since William and Kate's wedding on April 29, watched by an estimated two billion people around the world.
The event, celebrating the queen's 85th birthday, took place the day after her husband Prince Philip turned 90. He is the longest-serving consort in British history.
For the annual pageant, massed ranks of soldiers in the famous red tunics and bearskin hats of the British army march on Horse Guards Parade.
The Olympic beach volleyball competition will be held on the historic parade ground during the 2012 Games.
The pomp and ceremony of Trooping the Colour - a hangover from preparations for battle when colours or flags were "trooped" down the rank so soldiers could recognise them - marks the queen's official birthday.
Her actual birthday is on April 21 but traditionally the monarch has another in the summer months, because the weather is supposed to be better for open-air celebrations.
There were huge cheers from the crowd as the royals left Buckingham Palace.
The queen and Prince Philip - also wearing a bearskin - rode in an open phaeton carriage.
As regimental colonels, their eldest children, Prince Charles and Princess Anne, rode on horseback alongside William, as did the queen's cousin Prince Edward, Duke of Kent.
Catherine joined other royals including her brother-in-law Prince Harry in watching from a room that was once military hero the Duke of Wellington's office.
After the ceremony, the royals headed back to Buckingham Palace to gather on the balcony for the first time since William's wedding.
They watched a fly-past of aircraft ranging from World War II Spitfires and Lancasters to modern Typhoon fighters before the Red Arrows aerobatics display team left trails of red, white and blue smoke in the sky.
Thousands of well-wishers gathered outside the palace gates to see the royals.
Prince Philip received a new title for his 90th birthday Friday, as the forthright consort said he would finally scale back his workload.
The queen made him Lord High Admiral - the titular head of the British Royal Navy - partly in recognition of the promising seafaring career he gave up to spend a lifetime at her side.
He marked his birthday with a characteristic lack of fuss, hosting a charity reception and chairing a military conference.
