Spain's Crown Princess Leonor is about to turn 18, thrusting her into the spotlight as heir to the throne and raising questions about the role she will play as an adult royal.

Her birthday, on Tuesday, will be marked by a formal ceremony in the Spanish Parliament, at which she will swear allegiance to the Constitution before receiving the medals of Congress and the Senate.

Anticipating the event, the Spanish royal family has released a series of photos of the princess, many of them previously unpublished.

They include one of her on her first day of school, flanked by her mother, Queen Letizia, and her father, King Felipe VI, who was then still a prince himself.

Another shows her in 2010, clutching the World Cup trophy the Spanish men's football team had just won. Others show her alongside her younger sister Sofía.

Underlining the significance of her birthday, there will also be a reception in the Royal Palace in Madrid, followed by a family gathering in the El Pardo palace, just outside the capital.

The release of the photos and a series of recent appearances by the princess leading up to her birthday confirm that, after years of having her image carefully shielded, she is now becoming a very public figure.

"Leonor will need her own narrative," noted royal biographer Carmen Remírez de Ganuza, adding that she "will have to connect with her own digital generation".

While the exact nature of that narrative is not yet clear, the build-up to the princess's arrival as a senior royal has gone smoothly.

In May, she graduated from UWC Atlantic, a boarding school in the Vale of Glamorgan, Wales, where she had been studying for the International Baccalaureate. As she received her diploma, her fellow students whooped and cheered and her tutor praised her "unwavering passion for learning, for understanding people, and exploring diverse perspectives" as well as her sense of humour.

The Spanish media then closely followed the conclusion of the princess's basic training at an army academy in Zaragoza, where she has begun a three-year officer's course. Leonor, like her classmates, was seen performing drill dressed in beret and fatigues and receiving a ceremonial sword.

Her royal duties then came to the fore as she presided over her own Princess of Asturias awards on 20 October.

Decorating individuals from a variety of fields, including Hollywood actress Meryl Streep and Japanese novelist Haruki Murakami, Leonor assured those present that "I fully understand and am conscious of my duties and what my responsibilities entail".

As she praised Streep, she spoke of how the actor was able to shed her own persona in order to take on her roles "and do so throughout an impeccable career, with freedom, courage and sensitivity to the challenges of our time".

The princess could have been outlining the role she sees for herself as first in line to a throne which has faced some severe tests in recent years.

In 2017, for example, King Felipe took the unusual step of wading into the political sphere by speaking out against Catalan separatists who were attempting to break away from Spain. In 2020, Leonor's grandfather Juan Carlos, who had abdicated six years earlier and was mired in financial scandals, left the country to live in Abu Dhabi. Although the scandals have dropped away, he has lived there ever since.

But beyond Leonor's institutional position lies another, less solemn role as a figure orbiting Spain's celebrity universe.

Already there is talk of "Leonormania" in light of the interest in her rising profile. Earlier this year, there were rumours that she was romantically linked to Barcelona and Spain football player Pablo Martín Páez Gavira, known as Gavi.

Those reports turned out to be false, but they highlighted the appetite in some quarters for the princess to be a part of pop culture.

Paris Match ran a headline on the Bulgari earrings that Leonor had worn for the Princess of Asturias awards ceremony. Journalist Jesús Reyes has even written a book about Leonor through the lens of her taste in fashion, which he claims she has inherited from her mother.

"From her father, King Felipe, she has inherited his commitment to the Crown, his extremely polite manners [and] his constant smile and pleasantness," wrote Reyes. However, after her 18th birthday, Princess Leonor is likely to find that she will be much more than a purely institutional figure.–BBC