Crowds erupt as beaming Kate appears side by side with King & surrounded by her family on Buckingham Palace balcony

Trooping the Colour or ‘The King’s Birthday Parade’ is a military ceremony which dates back to the early eighteenth century or earlier, when the colours (flags) of the battalion were carried (or 'trooped') down the ranks so that they could be seen and recognised by the soldiers.

Since 1748, this parade has also marked the Sovereign's official birthday.

The honour to Troop their Colour rotates through the five regiments of Foot Guards, and this year it lies with Number 9 Company Irish Guards.

The Irish Guards were raised by Queen Victoria in 1900 and have provided almost 125 years of service to the nation.

This year marks the second Trooping the Colour of His Majesty’s reign.

The King attended his first Trooping the Colour in 1951, aged three, riding in a carriage with his grandmother, Queen Elizabeth The Queen Mother, and aunt, Princess Margaret. The King first rode in the parade as Colonel of the Welsh Guards in 1975.

By Ryan Merrifield

IT WAS pouring with rain as I joined crowds moving from Charing Cross Station towards the Mall around 9.30 this morning. 

A street vendor was selling umbrellas - plain black or with a Union flag pattern - for £8. He was making a killing. I bought one too.

Security staff in see-through waterproof ponchos were directing people down the steps ahead of the Duke of York statue. 

Some people stayed on the steps for a better view above the crowds.

It stopped raining briefly before the procession began down to Horse Guards. Two men in mock Irish Guard uniform were handing out leaflets and posing for photos with tourists outside the Institute of Contemporary Arts.

Isabel Parker, a 24-year-old therapist from Boston, US, had travelled from Amsterdam this morning and landed around 8.30am at Heathrow, then raced over for the procession. 

“I changed my flight a little bit earlier to be here,” she said, backpack on and holding a coffee cup. 

“I just saw that it’s happening and Kate’s coming. I really admire the way she’s handling the treatment and maintaining her privacy. 

“I respect her maintaining her poise and elegance. It’s important that she’s able to do these events, as long as she’s well.”

She added: “I landed about an hour and a half ago and dashed here. I’m very tired but London is lovely.”

Reema Dudehula and Kareen Budhrani, both 26, from Singapore, had ventured down after hearing about the event by chance.

Kareen works in London but friend Reema has been visiting from the pair’s homeland of Singapore for the past three weeks.

Reema said: “We only found out it’s the king’s birthday yesterday.”

Kareen added: “On my work calendar it always has the King’s birthday. It’s integrated with the Google calendar, so I thought what's going on for it?

“This is unfortunate on his birthday,” she said of the rain.

Both agreed their favourite royal is the late Princess Diana.

Referring to Kate’s return to duty, Reema said: “I’ve not been too invested but I did hear a lot about the chatter about her disappearance. 

“It was quite a sensation on social media. I just hope she’s well.”

Looking at the rain, she added: “Is this usually how your summer is?”

Moving around the lines of royal fans, some people commented that it wasn't as busy as they expected this year, putting it down to the rain meaning local Londoners may not have been as keen. 

Others said they were pleased with how many toilet facilities there were. 

Teenage major royalist Ben McLean told me it had been 33C last year and everyone had been sweating.

The crowd 'ooo'd' as an unruly horse bucked its rider about a little ahead of the King's carriage. 

And they roared and whooped as Kate went past. 

Listening to onlookers, many were gushing over Camilla and how good it was to see her. 

She got nearly as much praise as the Princess of Wales.

Ben, 15, from Welwyn Garden City, Hertfordshire, was right at the front by the railings with his mum and friends.

They had several Union flags and were sitting on camp chairs.

“It was very cool to see Kate on her first engagement since December, especially with all the conspiracy theories,” Ben said. 

“We were expecting the carriage to be open top but because of the rain I guess they closed it.”

However, he said his favourite royal is Queen Camilla, describing her as “very hardworking”.

On seeing the carriages go by, he said he believes King Charles smiled and pointed at his group’s display of flags up.

“Last year was very hot, we were sweating,” he recalled.

Married couple Daigo, 52, Rie Nakauura, 56, originally from Japan, had previously called London home and had returned for the procession and to visit the Cotswolds.

They now live in Singapore.

Daigo said: “It was very nice to see Kate, we didn’t expect it. She looked very well. We’re just happy to be here for the event. We are very big fans.”

Asked if any of the royals waved back, he said: “I don’t know, she (Rie) was concentrating so much on the video we will have to watch back what actually happened.”

Sara Makhoul, 23, and Nicolas Chauveau, 25, students from Paris, had, like Isabel, rushed in by plane to see Kate but missed her.

Sara said: "We flew here very early in the morning, we just arrived. 

“I can't believe we missed it. It was raining in Paris when we left too. 

“It was great that Kate was able to take part, we heard people cheering. We just made it to the front.”

Meanwhile, Spanish friends Eva Urbano, 34, Rosa Ordonez, 32, and Elvira Herrera, 34, are visiting London for three days, having arrived last night. 

They just happened on the parade while wandering around nearby.

Eva, an engineer, said: "We arrived yesterday evening. We are just visiting and we found this event just by chance. 

“London is very rainy, it is not the sort of weather we're used to. It was 30C when we left, very sunny. 

“We didn't know Kate was coming back today but we heard people talking, so it's very exciting."

A couple who'd travelled from Essex struggled to see from a few rows back and joked they needed to erect big screens or that they should have just watched it at home. 

They left before the King came back towards Buckingham Palace. 

By then it was lashing down with rain, and people were sheltering wherever they could. Under the lip of the canopy outside the ICA and Royal Society, under trees. 

People jumped as thunder struck just as Charles made his return ride - then they cheered before filing inside the ICA's cafe.  

*See photos of everyone we spoke to at the bottom of the page

THE Royals were one big happy family on the Buckingham Palace balcony as the Princess of Wales made an emotional one-off appearance.

This was a brave return to public life for Catherine, who has valiantly battled cancer for the last three months.

She did not have to be at Trooping the Colour and no one would have blamed her for staying away.

But she still chose to attend.

It is a measure of just how much her duty and family mean to her.

I have not seen the Princess of Wales in person since her last public engagement on Christmas Day, more than six months ago.

Yesterday she looked very well and, crucially, very healthy too.

While the photo released on Friday by Kensington Palace was a solemn snap, yesterday Catherine beamed with joy – her smile will undoubtedly warm the nation’s heart.

Accompanied by William, who has soldiered on alone while supporting his sick wife, and her adorable children, the whole group looked relaxed and united throughout one of the most important days of the year for the Royal Family.

It was also lovely to see Catherine exchanging words with her father-in-law King Charles.

Both of them battled hard to return to their duties and even through a long lens you can tell they have genuine warmth for each other.

The only downside was the classically British weather.

It was cold.

It was wet.

My jacket and my camera were soaked.

Next Thursday will be the longest day of the year but the driving rain made me feel like I was in the middle of January.

Yet the moment the Princess emerged to wave and smile, it made bearing the downpour worthwhile.

There were a lot of smart outfits on show – it was a military parade after all – but the Princess of Wales’ stunning white dress was a cut above everyone else’s.

Almost every camera there was fixed on her and with exceptional taste she picked out a dress that could be seen down The Mall by thousands of well-wishers.

This was a remarkable return by a remarkable woman and I'm sure it would’ve meant the world to have her family by her side.

So it’s no surprise that she didn’t stop smiling throughout.

The Glass Coach, which Princess Kate travelled in today, was built in 1881 and purchased for the Coronation of George V in 1911.

The Glass Coach has been used most famously at many royal weddings. It carried Queen Elizabeth II, then Princess Elizabeth, in 1947 to Westminster Abbey from Buckingham Palace on her wedding day.

In 2012, it was also used to convey Queen Elizabeth II and the Duke of Edinburgh to and from Horse Guards Parade for Trooping the Colour.

When not in use, the coach is normally on public display in the Royal Mews.