You can't choose when your birthday falls, and sometimes, as Queen Camilla knows today, duty calls.

The royal, who is celebrating her 77th birthday, at least got to wear her finery -including the royal collection's Diamond Diadem tiara - as she stood by the king's side at the State Opening of Parliament in Westminster this morning.

The Queen donned an elegant white ankle-length gown and matched the regal tiara with a pair of spectacular earrings and the late Queen Elizabeth II's 28-diamond Coronation Necklace, estimated to be worth around £72,000. 

The royal finished the look with a co-ordinating silver clutch bag and matching low heeled shoes; Camilla is still nursing an ankle injury picked up on the first day of King and Queen's royal tour of the Channel Islands this week. 

Later, Camilla also wore a crimson Robe of State, which was made for Elizabeth II's coronation in 1953, after putting it on in the Palace of Westminster's historic Robing Room. 

Queen Camilla is celebrating her 77th birthday today but public service trumped any major celebration, as she accompanied the King to the Houses of Parliament for the State Opening of Parliament

Queen Camilla is celebrating her 77th birthday today but public service trumped any major celebration, as she accompanied the King to the Houses of Parliament for the State Opening of Parliament

Camilla looked elegant on her birthday, wearing the royal Diamond Diadem as she arrived at the Houses of Parliament earlier today

Camilla looked elegant on her birthday, wearing the royal Diamond Diadem as she arrived at the Houses of Parliament earlier today

The diadem tiara is rarely seen on royals but comes out for state occasions and Her Majesty Queen Camilla is the fifth queen consort to wear a crown that was originally created for a king - George IV.

Set with 1333 diamonds and 169 pearls, the tiara's narrow band is edged on both sides with the pearls, and surmounted by four crosses-pattées, the front cross is set with a four carat pale yellow brilliant-cut diamond from Brazil.

Between each cross are the diamond set national emblems of England, Ireland and Scotland: roses, shamrocks and thistles. 

The Coronation Necklace has an equally refined backstory; it was originally made for Queen Victoria in 1858 and comprised 28 diamonds, including the 22.48-carat Lahore Diamond gemstone pendant, which Queen Camilla detached for today's wearing. 

The couple have just returned from the Channel Islands; yesterday when offered an early birthday wish, the Queen told one member of the public on Guernsey: 'Thank you. Sometimes you ought to forget them!'

The couple have just returned from the Channel Islands; yesterday when offered an early birthday wish, the Queen told one member of the public on Guernsey: 'Thank you. Sometimes you ought to forget them!'

Camilla wore the same necklace as she did at last year's State Opening of Parliament, the late Queen Elizabeth II's beautiful 28-diamond Coronation Necklace

Camilla wore the same necklace as she did at last year's State Opening of Parliament, the late Queen Elizabeth II's beautiful 28-diamond Coronation Necklace

In the historic speech as the country welcomes a new government, King Charles revealed Sir Keir Starmer's plans for Britain in the first speech from the throne under a Labour government for 14 years.

On a day filled with pomp and pageantry, Charles opened the speech by saying Labour's programme will be 'based upon the principles of security, fairness and opportunity for all'.

The King and Queen entered the House of Lords for the historic day following a resplendent horse-drawn procession down the Mall.

The Monarch and Queen were then taken to Parliament in the Diamond Jubilee State Coach, pulled by six grey horses in the glorious sunshine.

They arrived to gun salutes, bell chimes and cheers from royal fans as they were welcomed through the gates of the Sovereign's Entrance - a doorway that is reserved for the monarch.

It's thought the King and Queen will enjoy a low-key birthday celebration for Camilla later in the day

It's thought the King and Queen will enjoy a low-key birthday celebration for Camilla later in the day

Set with 1333 diamonds and 169 pearls, the diadem tiara is rarely seen on royals but comes out for state occasions

Set with 1333 diamonds and 169 pearls, the diadem tiara is rarely seen on royals but comes out for state occasions

The King and Queen were seen holding hands as they led a royal procession before the King gave his speech on a historic day that welcomes in a new government

The King and Queen were seen holding hands as they led a royal procession before the King gave his speech on a historic day that welcomes in a new government

The King and Queen recently returned from their two-day royal visit to Jersey, pictured: King Charles III and Queen Camilla in the Royal Gallery during the State Opening of Parliament

The King and Queen recently returned from their two-day royal visit to Jersey, pictured: King Charles III and Queen Camilla in the Royal Gallery during the State Opening of Parliament

Britain's King Charles and Queen Camilla walk through the Royal Gallery on the day of the State Opening of Parliament

Britain's King Charles and Queen Camilla walk through the Royal Gallery on the day of the State Opening of Parliament

They were accompanied by a Sovereign's Escort of the Household Cavalry as they travelled in the carriage procession to the House of Lords.

The black and gilded Diamond Jubilee State Coach is the newest in the Royal Mews. It has shock absorbers to stop it from swaying, and heating, internal lights and power windows. It was used by the King and Queen on their journey to their coronation in 2023.

The King is wearing his Admiral of the Fleet Royal Naval Number 1 Dress with cap and sword. 

In the Robing Robe at the House of Lords, Charles put on the Imperial State Crown and his crimson Robe of State, which was made for his grandfather George VI's coronation in 1937.

Britain's King Charles III, wearing the Imperial State Crown and the Robe of State, sits alongside Britain's Queen Camilla, wearing the George IV State Diadem before reading the King's Speech

Britain's King Charles III, wearing the Imperial State Crown and the Robe of State, sits alongside Britain's Queen Camilla, wearing the George IV State Diadem before reading the King's Speech

Queen Camilla seen arriving at the House of Lords at the Palace of Westminster with the King this morning

Queen Camilla seen arriving at the House of Lords at the Palace of Westminster with the King this morning 

The King and Queen pictured leaving the House of Lords following King Charles speech

The King and Queen pictured leaving the House of Lords following King Charles speech

Charles and Camilla are just returned from a two-day trip to the Channel Islands and speaking to well-wishers on Guernsey yesterday, it seems the Queen had resigned herself to a day of public service. 

Camilla, who has been troubled by a sprained ankle in recent days, told members of the public that she wouldn’t have the chance to put her foot up and rest because she was due to attend today's State Opening of Parliament. 

When offered an early birthday wish, the Queen told one member of the public on Guernsey: 'Thank you. Sometimes you ought to forget them!'