Lady Louise Windsor stuns in floral dress she wore to King's Coronation as she joins equally-elegant Duchess of Edinburgh at Trooping the Colour

The Duchess of Edinburgh and her daughter Lady Louise looked stylish as they joined other members of The Firm at Trooping the Colour today.

The annual event, a major highlight of the royal calendar, celebrates the birthday of the reigning monarch in the UK and has been held every year for the past 260 years.

Sophie, 59, was dressed for the occasion, donning a bright yellow ensemble, channelling Spring on a rainy day in London. 

She was joined by her daughter, Lady Louise, who looked graceful in a white chiffon tea dress adorned with blue flowers - a frock she previously donned for the King's Coronation last May.

The dress she wore is from Suzannah London and she paired the standout garment with a light blue fascinator and silver pearl drop earrings. 

Lady Louise , 20, who is currently studying at the University of St Andrews, did not attend Trooping the Colour last year.

Sophie was pictured next to her husband, the Duke of Edinburgh, who looked dapper in his dashing red uniform, displaying his medals.

The Princess of Wales rode in a separate car with her husband Prince William and their children, Prince Louis, Prince George and Princess Charlotte. 

Kate was dressed in a white ensemble, featuring a cream fascinator and a pair of elegant pearl earrings. 

The Princess of Wales smiled as she travelled in a carriage with her children, who waved to crowds of well-wishers and royal fans. 

Today's ceremony, which marked King Charles' second Trooping the Colour, saw His Majesty, 75, greeted by a royal salute, before he carried out an inspection of the troops of fully trained and operational soldiers wearing the ceremonial uniform of red tunics and bearskin hats.

Next, massed bands performed a musical 'troop', while the escorted Regimental Colour was carried down the ranks. After the Foot Guards and the Household Cavalry marched past His Majesty, The King's Troop and the Royal Horse Artillery, Charles, 75, rode back to Buckingham Palace at the head of his Guards, before he took the salute at the Palace.

This was followed by perhaps the most eagerly awaited moment of the day: the RAF fly-past which was watched by members of the Royal Family who had gathered on the palace balcony. 

Fans had started gathering on The Mall early this morning, keen to spot members of the Royal Family on Buckingham Palace's balcony.

Many were particularly excited following the Princess of Wales' announcement yesterday that she would be making her first public appearance by joining her family at Trooping the Colour.

She announced the news in a frank and open statement, in which she revealed she has both 'good and bad' days, and that she is pleased she's able to make the most of those days when she is feeling well. 

Kate, who has been receiving treatment for an undisclosed form of cancer since late February, rode in a carriage alongside her three children, Prince George, Princess Charlotte and Prince Louis, for the traditional procession through London.

Following the carriage ride, she joined King Charles and Queen Camilla, as well as her husband Prince William and other royals on the palace balcony for the famous RAF flypast.

Following weeks of speculation around whether the Princess of Wales would attend today's event, last night, Kate issued a candid statement outlining her personal cancer journey and said she is experiencing 'good days and bad days' as she undergoes chemotherapy.

But she has begun to work from home, undertaking meetings with her foundation and Kensington Palace team, and hopes 'to join a few public engagements over the summer' but stressed 'I am not out of the woods yet'.

The princess has been receiving treatment for an undisclosed form of cancer since late February and her decision to choose a major national event today to return briefly to the public spotlight, the first time since Christmas Day, was welcomed by the King.

A new photograph of the royal, taken earlier this week in the grounds of the Windsor Castle estate, shows Kate in a smart casual outfit standing in a tranquil setting against a weeping willow tree near a body of water.

She said in her statement: 'I am making good progress, but as anyone going through chemotherapy will know, there are good days and bad days. On those bad days you feel weak, tired and you have to give in to your body resting. But on the good days, when you feel stronger, you want to make the most of feeling well.

'My treatment is ongoing and will be for a few more months. On the days I feel well enough, it is a joy to engage with school life, spend personal time on the things that give me energy and positivity, as well as starting to do a little work from home.'

She added: 'I'm looking forward to attending the King's Birthday Parade this weekend with my family and hope to join a few public engagements over the summer, but equally knowing I am not out of the woods yet.

'I am learning how to be patient, especially with uncertainty. Taking each day as it comes, listening to my body, and allowing myself to take this much needed time to heal.'

A Buckingham Palace spokesperson said: 'His Majesty is delighted that the princess is able to attend tomorrow's events, and is much looking forward to all elements of the day'.

A time frame has not been set for Kate's return to a full schedule of public engagements as she is being given time to convalesce and recover before full-time work.

Trooping will be a special event for the princess as Number 9 Company, Irish Guards, a regiment she represents as Colonel, will be Trooping their King's Colour on Saturday, but Lieutenant General Sir James Bucknall will take the salute on her behalf.

The King, who is also undergoing cancer treatment, will not ride during the ceremony but will inspect the troops formed up in Horse Guards Parade in Whitehall from a carriage.

The many royal fans who had lined The Mall in the hopes of spotting members of the family were also joined by a number of protestors.

Scotland Yard put in place a 'substantial' policing operation for the event, with anti-monarchy group Republic allowed to protest but banned from using amplified sound.

Scotland Yard imposed a condition under Section 14 of the Public Order Act 1986 prohibiting protesters from using systems to amplify sound 'within the footprint' of Trooping the Colour between 8am and 3pm. 

Ahead of the event, Chief Superintendent Colin Wingrove said: 'Trooping the Colour holds national significance and as you would expect with this ceremonial event there is a substantial security operation to ensure everyone who attends and participates can do so in a safe and secure way.

'Alongside colleagues at the Ministry of Defence and the Royal Parks, our policing plan has focused on achieving this aim.'

He added: 'It's imperative this event is safe, which is why along with our partners we have considered factors, such as how amplified noise could disrupt and impact mounted regiments taking part.

'We have also taken into account the views of Republic. Our concern, along with partners, is that amplified noise could cause a public safety issue and serious disruption to the event and crowds attending.

'That is why the Met has taken a considered decision to impose a condition prohibiting amplified sound.'

In response, Republic, which campaigns for the abolition of the monarchy and its replacement with a directly elected head of state, said the protest will go ahead without amplified sound.

Chief executive Graham Smith said: 'We don't agree with their reasons but we have to go along with it because otherwise we'll be arrested.

'It isn't a big problem, we've got quite loud voices.'