Princess Leonor received a monumental reception from royal fans on her 18th birthday today.

Spain’s capital was bustling with huge crowds who gathered outside the Congress of Deputies in Madrid to show their support for Leonor after she took an oath of allegiance to the Spanish Constitution. 

Royal fans swarmed around the car where the queen-in-waiting sat with her younger sister, Infanta Sofia, 16.

The princess delighted fans as she smiled towards the crowds as they gathered around the car to catch a glimpse of the heir. 

A sea of Spanish flags of all shapes and sizes accompanied the warm reception from royal fans.

Princess Leonor (right) and Infanta Sofia (left) smiled and waved at the bustling crowds after Leonor swore an oath of allegiance of the Constitution before the Cortes Generales on her 18th birthday today

Royal fans swarmed around the car where the queen-in-waiting sat with her younger sister, Infanta Sofia, 16

Leonor (left), King Felipe VI of Spain (centre left), Queen Letizia of Spain (centre right) and Princess Sofia of Spain (right) watched the military parade, which marked the special occasion

Madrid residents witnessed a series of special events in the country’s capital to honour Leonor’s 18th birthday.

The crowds waved bright red and yellow flags after volunteers distributed more than 7,500 Spanish flags across the city for residents to wave in appreciation of Leonor.

After the teen royal swore allegiance to the throne to preserve the Magna Carter as the successor of the Head of State, she observed a military parade in the streets of Madrid, the city where Leonor was born and has spent most of her life.

An honour guard of the Municipal Police, chaired by the vice mayor of Madrid, which included the Cavalry Squadron and the Municipal Police Music Band, was deployed in the Plaza de la Villa.

The heir to the throne watched the parade alongside her parents, King Felipe VI, 55, and Queen Letizia, 51, and Infanta Sofia.

The Spanish royal family also joined the parade from their cars and charmed fans as they waved and smiled while driving by.

Infanta Sofia, who is currently following in her sister’s footsteps by attending her previous school, UWC Atlantic College in Wales, waved at the crowds who turned out to celebrate her sister’s coming of age.

Meanwhile, Leonor sat by with a wide grin across her face as she looked on at the supporters.

Spain’s capital was bustling with huge crowds who gathered to support Leonor after she took an oath of allegiance to the Spanish Constitution 

To mark the occasion, Felipe awarded Leonor with the Collar of the Order of Charles III (Carlos III), Spain’s highest civil honour

Stepping on to the stage at the House of Parliament in Madrid this morning, Princess Leonor looked calm and composed despite the historic weight of the moment she officially became Spain’s future Queen. 

Today on her 18th birthday, the teenager swore allegiance to the Spanish Constitution, meaning that she can now officially act as regent in the absence of her father King Felipe. 

When she ascends the throne, Leonor will be Spain’s first queen regent in for 150 years, but even more significantly she is viewed as a figure who will complete her father’s work of distancing himself from the scandal that engulfed her grandfather, King Juan Carlos. 

It’s a lot of expectation for any young woman to contend with, but Princess Leonor betrayed only the slightest hint of nerves in a touching moment where she appeared to glance to her mother Queen Letizia and younger sister Infanta Sofia, 16, for reassurance.

An honour guard of the Municipal Police, chaired by the vice mayor of Madrid, which included the Cavalry Squadron and the Municipal Police Music Band, was deployed in the Plaza de la Villa

The cavalry squadron donned traditional attire and proudly held Spanish flags as they rode through Madrid’s centre 

Leonor and Sofia waved to the crowd from their car as they left the ceremony at the Congress of Deputies 

A cavalry squadron was deployed through the centre of Spain’s capital to mark the special occasion 

Spanish royal guards donned traditional uniform for the special occasion, and rode white horses through the city centre 

Her confidence has no doubt been honed by a stint away from her family at boarding school – the Welsh Hippie Hogwarts – as well as military training and giving her first public speech aged 13 to mark the 40th anniversary of the Spanish constitution.

As she swore allegiance to the Spanish Constitution in Parliament with her family and government representatives watching on, Leonor’s experience in public speaking was clear to see, with a proud and unwavering delivery. 

In a speech delivered to the nation after the ceremony, the Princess once again stated her commitment to the Spanish people, and in turn asked Spaniards to trust in her as she steps up her role and becomes a Queen-in-training. 

And a touching yet poignant moment came when the King presented his daughter with the Collar of the Order of (Carlos III) which is the highest civil honour in Spain/

Leonor looked regal in a white suit, with her hair pulled back into a low, sleek ponytail, and her make up neutral and understated.

Princess Leonor smiled at the crowds from her car as members of the public gathered to catch a glimpse at the queen-in-waiting 

Royal guards rode on white horses through the town centre to commemorate Leonor’s 18th birthday

Princess Leonor of Spain (left) has sworn allegiance to the Spanish Constitution to mark her 18th birthday, meaning she can now officially act as regent in the absence of her father King Felipe (right)

ollowing the ceremony, the 18-year-old Princess kissed her mother Queen Letizia, 51, and father King Felipe, 55, on the cheek, as the proud parents held her arms in a supportive gesture. 

Throughout, the King and Queen watched on – and at the end of the ceremony when Leonor was presented with medals of Congress and The Senate, her father King Felipe offered a sweet fatherly gesture.

The monarch stepped in to adjust his eldest daughter’s ponytail so the heavy-looking medals could rest more comfortably around her neck. 

It was a fleeting gesture that did not take any attention away from the woman of the hour, but an indication that the monarch is still there to guide his daughter as she steps up in her responsibilities.

As the Spanish princess and heir to the throne stepped up to address the nation following the ceremony, she asked Spaniards to put their trust in her

In a poignant moment, King Felipe adjusted the Collar of the Order of Charles III (Carlos III) on his daughter’s shoulders at the end of the ceremony

The Spanish heir to the throne and her mother looked elegant as they walked through Congress

The Spanish royal family were in high spirits after the ceremony, with Queen Letizia beaming as she strolled along next to her husband and daughters

Princess Leonor’s proud parents and younger sister Infanta Sofia, 16, watched on in earnest as the heir to the throne addressed the nation

King Felipe could not contain his pride as he applauded his daughter following the speech

Princess Leonor kissed her mother on the cheek and took her arm in a gesture of support after swearing allegiance to the Constitution

The ceremony takes place in the Spanish Lower House of Parliament in Madrid, the city where Leonor has spent most of her life

As the Spanish royals descended the steps outside of the building at the end of the ceremony, Leonor remained close in stature to her sister Infanta Sofia

A crowd at Plaza de Puerta del Sol in Madrid gather to watch the Princess and her little sister Infanta Sofia arrive in a Rolls Royce

Queen Letizia beamed as she stood with her family and Spanish Prime Minister Pedro Sanchez

Princess Leonor, the Princess of Asturias, was awarded with the medals of Congress and the Senate before the Cortes Generales, in the Congress of Deputies

Princess Leonor has sworn allegiance to the Spanish Constitution to mark her 18th birthday in Madrid 

The Princess and future Queen of Spain swore allegiance to the Constitution as part of the Magna Carta Ceremony, carried out by her father 27 years ago, as she marks her 18th birthday

Ahead of the ceremony in the Spanish capital, crowds of royal fans lined the streets to join in on the celebrations – reflecting the young royal’s popularity among the people of Spain.

Newspaper El Espanol reported that the 18-year-old is Spain’s most popular royal, after a poll revealed she is even more highly regarded than her father King Felipe.

The enthusiasm for the Spanish royal family and its younger generations is a far cry from discontent that spread around the nation following the abdication of Leonor’s grandfather, King Juan Carlos.

The former monarch 84, who currently lives in Abu Dhabi, stepped down after nearly 40 years on the throne in 2014 after his daughter’s husband became embroiled in a controversial elephant hunting scandal.

Just this month, the former King won his bid to end a £126 million High Court battle in the UK with his Danish ex-lover who accused him of spying on and harassing her.

Businesswoman Corinna zu Sayn-Wittgenstein-Sayn, who is in her late 50s, claimed the former royal had caused her ‘great mental pain’.

Juan Carlos, 85, has denied wrongdoing and disputed the claims made against him, arguing they are not ‘viable’.

Despite several years of scandal at the heart of the Spanish monarchy, the royal family today appeared to enter a new era, with King Felipe, Queen Letizia, Princess Leonor and Infanta Sofia welcomed in the centre of Madrid by roaring crowds.

The Magna Carta ceremony marks 37 years since Leonor’s father, King Felipe, swore the oath on 30 January 1986 in the same Palacio de las Cortes de la Carrera de San Jerónimo.

The oath taken by Leonor before the Cortes Generales preserves the Magna Carta as the successor of the Head of State. 

In addition to Leonor swearing an oath to the Spanish Constitution, the mayor has invited residents to join in on the celebrations.

Volunteers have distributed more than 7,500 Spanish flags across the city for residents to wave in appreciation of Leonor.

Later on in the day, an honour guard of the Municipal Police, chaired by the vice mayor of Madrid, which will include the Cavalry Squadron and the Municipal Police Music Band, will be deployed in the Plaza de la Villa.

José Luis Martínez-Almeida said: ‘As mayor of the capital of Spain, I invite you to actively participate so that Madrid is once again up to par and that this historic ceremony is an eloquent icon of the loyalty and affection that we Madrid residents feel for the Royal Family in general and for Mrs. Leonor in particular on this special day of her life.

‘May our streets and balconies be decorated with the colours of the national flag, “a symbol that unites all Spaniards,” as the King recalled in the recent Flag oath of the Princess of Asturias in Zaragoza.’

Upon entering the Palacio de las Cortes de la Carrera de San Jerónimo, Princess Leonor waved at royal fans

The Spanish royal family and Prime Minister Pedro Sanchez arrived at the ceremony