Lilian was initially educated in English, but, upon her parents' return to Belgium, she attended a school in Ostend, where she learned Flemish. She continued her studies in French in Brussels. She completed her education by attending a finishing school in London, the Holy Child. In addition to academic work, Lilian participated extensively in sports, such as skiing, swimming, golfing, and hunting. Above all, however, she enjoyed, as did her father, literature and the arts. At the age of 20, Mary Lilian Baels, who had grown up into a young woman of great beauty, intelligence, and accomplishment, was presented to King George V and Queen Mary of England at Buckingham Palace.
In 1933, Lilian met her future husband, King Leopold III of the Belgians, then still Crown Prince of Belgium. The students at the Institute of the Sacred Heart in Brussels, where Lilian was enrolled at the time, had been allowed to attend a military review conducted by King Albert, not far from the school. During the review, Prince Leopold, on horseback, paraded at the head of his battalion, saluting his father, the king. Following the ceremony, when the students in her class were given as homework the task of writing an essay on a topic of their choice, Lilian chose as her topic Prince Leopold. A few years later, when Governor Baels took his daughter to a public ceremony, she had the occasion to meet King Leopold, who presided at the event, for the second time. In 1937, Lilian and her mother met the King, now a widower, again on another ceremonial occasion. Soon afterwards, Leopold contacted Governor Baels to invite him and his daughter to join him in a golfing party the next day. Lilian also saw the King in 1939 at a garden-party organized in honor of Queen Wilhelmina of the Netherlands, and later at the golf course at Laeken, where she was invited to lunch by Queen Elisabeth of Belgium, King Leopold's mother. A final golf party near the Belgian coast occurred in May, 1940, shortly before the Nazi invasion of Belgium. The night of the party, clouds appeared threateningly in the sky above the sea. King Leopold saw this as a prefiguration of the threat of invasion which hung over Belgium. Lilian was quite struck with the prophetic character of this remark, as the Nazis attacked Belgium only a few days later, on May 10, 1940.
Following the Nazi invasion of Belgium, Lilian's mother put herself at the service of the Red Cross during the Belgian and Allied military campaign against the invaders. Lilian helped her mother actively in her new role, transporting Belgian and French wounded by car to the hospital of St. John in Bruges, where there were also many refugees to care for. Lilian was called upon to help evacuate the elderly from the hospice of Alost, which was inside the combat zone, exposed to enemy fire. Despite the dangers, Lilian managed her task with energy and dedication. Meanwhile, her father, Governor Baels, circulated constantly to alleviate the plight of his invaded province. On May 18, Henri Baels went in search of the Minister of the Interior, thinking he had left for France, in order to obtain his signature for an important relief measure. On his journey, however, Governor Baels had a car accident and injured his legs. He was admitted to a hospital in Le Havre. As the military situation in Belgium headed towards disaster, his wife decided to bring her daughters to safety in France, and Lilian drove the family car on the trip. Governor Baels' wife and daughters managed to meet up with him again, by pure chance, in a hospital in Poitiers. Baels was subsequently, and unfairly, accused of having abandoned his post as Governor without justification by fleeing to France. He succeeded, however, in obtaining an audience with the King, following the capitulation of the Belgian army on May 28, 1940, and the King's own imprisonment by the Germans at Laeken Castle. Baels and his daughter Lilian, who drove him to the audience, explained the real circumstances of his departure from Belgium, and the Governor was thus vindicated. Subsequently, Lilian and her father returned to France and occupied themselves with the care of Belgian refugees in the region of Anglet. Henri Baels was accused, after Belgium's liberation, of collaborating with the Nazis during the war, but this is clearly false, since he did not act as governor during the occupation and lived in France throughout the entire period.
In 1941, Queen Mother Elisabeth of Belgium sent a letter to Lilian, inviting her to come visit her at Laeken. Here Lilian met King Leopold, now a prisoner of war, yet again. This meeting was followed by several other visits to Laeken, with the result that Leopold and Lilian fell in love. Nonetheless, when Leopold proposed marriage to Lilian in July 1941, the young woman, aged 24, was frightened, anticipating the marriage would lead to political controversy, and not feeling adequate to succeed Queen Astrid, Leopold's popular, and, by now, almost legendary, first wife who had died tragically in a car accident in 1935. Queen Elisabeth, however, persuaded Lilian to accept the King's offer, citing Leopold's need for a supportive wife and his children's need for a loving mother, especially given the family's tragic loss of Queen Astrid and the current atmosphere of anxiety, oppression, and insecurity during the war. Lilian agreed to marry the King, but declined the title of Queen. Instead, the King gave her the unofficial title "Princess of Réthy." It was agreed that any descendants of the King's new marriage would be excluded from succession to the throne. Leopold and Lilian initially planned to hold their official marriage after the end of the war and the liberation of Belgium, but in the meantime, the religious and moral convictions of the couple required that they be husband and wife "before God." Thus, a secret religious marriage ceremony took place on September 11, 1941, in the chapel of Laeken Castle, in the presence of Queen Elisabeth, Henri Baels, and Cardinal van Roey, Archbishop of Mechelen and primate of Belgium. Although Lilian and Leopold had originally planned to postpone their civil marriage until the end of the war, Lilian was soon expecting her first child, necessitating a civil marriage, which took place on December 6, 1941. The civil marriage automatically made Lilian a Princess of Belgium. Lilian proved a devoted wife to the King and an affectionate and vivacious mother to his children by Queen Astrid. The royal children were extremely fond of her, immediately beginning to call her "maman".
When the civil marriage of Leopold and Lilian was made public by Cardinal van Roey, in a pastoral letter read throughout Belgian churches in December, 1941, there was a mixed reaction in Belgium. Although the opposite is often asserted, there was actually a great deal of sympathy for the new couple among the Belgian population. The palace at Laeken received numerous messages of congratulations and flowers from the populace. The King also received the good wishes of a group of Belgian ministers-in-exile in France. In addition, however, the marriage was exploited by political propagandists hostile to the King. In newspaper articles, pamphlets, and graffiti, these authors presented the marriage as incompatible with the King's status as a prisoner-of-war and his stated desire to share the hard fate of his conquered people and captive army, and as a betrayal of Queen Astrid's memory. They also branded Lilian as an intriguing social-climber. These accusations ignored the fact that many of the Belgian prisoners-of-war were actually released and allowed to return home during the war, enabling them to enjoy family life, and also the fact that Lilian had chosen to unite her fate to that of the King at a very troubled and insecure time, and had expressly renounced the title of Queen. Nonetheless, the accusations, over the course of the protracted political controversy surrounding the King's actions during the War, the "Royal Question" that eventually led to his abdication in 1951, turned many Belgians against Princess Lilian.
In 1944, the Belgian royal family was deported to Nazi Germany, where they were kept, strictly guarded by 70 members of the SS, under harsh conditions. The family suffered from a deficient diet and lived with the fear that they would be massacred by their jailers, as an act of revenge on the part of the Nazis, angered at their defeat (by now becoming increasingly certain ) by the Allies, or that they would be caught in the cross-fire between Allied forces and their captors, who might try to make a desperate last stand at the site of the royal family's internment. The family's fears were not unfounded. At one point, a Nazi official tried to give them cyanide, pretending it was a mixture of vitamins to compensate for the captives' poor diet during their imprisonment. Lilian and Leopold, however, were rightly suspicious and did not take the pills or give them to their children. During their period of captivity in Germany, (and later Austria ), Leopold and Lilian jointly homeschooled the royal children. The King taught scientific subjects; his wife, arts and literature. In 1945, the Belgian royal family was liberated by the troops of the American General Patch, who thereafter became a close friend of King Leopold and Princess Lilian.
Following his liberation, King Leopold was unable to return to Belgium (by now liberated as well ) due to a political controversy surrounding his actions during the conflict. A group of Belgian ministers and other politicians were accusing him of having betrayed the Allies by a supposedly premature surrender in 1940, and of collaborating with the Nazis during the occupation of Belgium. There were also many personal attacks on the King and his second wife, Princess Lilian. In 1946, a juridical commission was constituted, to investigate the King's conduct during the war and occupation. During this period, the Belgian royal family lived in Prégny, Switzerland, in exile, and King Leopold's younger brother, Prince Charles of Belgium, was made Regent of the country. Leopold was eventually completely exonerated of all charges, and was able, in 1950, to return to Belgium and resume his reign. Political agitation against the King continued, however, leading to civil disturbances. As a result, in 1951, in order to avoid tearing the country apart, and to save the embattled monarchy, King Leopold III of the Belgians abdicated in favor of his 21-year-old son, Prince Baudouin. The ex-King Leopold and Princess Lilian continued to live in the royal palace at Laeken until the marriage of Baudouin to Dona Fabiola de Mora y Aragon in 1960. During this period, Lilian presided over court life with firmness and refinement.
In 1960, following the marriage of King Baudouin, Leopold and Lilian moved out of the royal palace to a government property, the estate of Argenteuil, Belgium. Lilian employed excellent designers to transform the dilapidated mansion on the property into a distinguished and elegant residence for the ex-King. Argenteuil became a cultural centre under the auspices of Leopold and Lilian, who cultivated the friendship of numerous prominent writers, philosophers, scientists, mathematicians, and doctors. Leopold and Lilian also traveled extensively all over the world. Following her son Alexandre's heart surgery in the United States during his childhood, Princess Lilian became very interested in medicine, and, in particular, in cardiology, and founded a Cardiological Foundation which, through its work, has saved the lives of several thousand people. Both before and after her husband's death in 1983, Lilian pursued her interests in intellectual and scientific spheres with great energy and passion.
Lilian was known as a woman who was terribly strict and demanding towards herself, and, a result, as one who could, on occasion, be excessively severe with others as well. She was also, however, known and loved by her circle of close friends as a woman of great beauty, charm, intelligence, strength of character, kindness, generosity, humor and culture. She was admired for the steadfast courage and dignity with which she faced many personal attacks and revilement, both during the Royal Question and for decades afterwards. Leopold loved Lilian very much and called her "Lil" as a nickname, while she called him "Léo". In response to a series of personal attacks on Lilian, Leopold publicly paid tribute to her tenderness and devotion as a wife and as a mother to his children by Queen Astrid. Lilian was famous for her glamorous style of dressing, which was later imitated by Jacqueline Kennedy.
The three children of King Leopold III and his second wife, Princess Lilian of Belgium, are:
Princess Lilian died at the Domaine d'Argenteuil in Waterloo in 2002 and was buried, contrary to her wish, in the royal crypt of the Cathedral of Our Lady, Laeken, Belgium. Before her death, she had expressed the desire to be buried at Argenteuil, under the weeping willow she and King Leopold had planted at Laeken Castle on the day of their religious marriage (September 11, 1941) and which they had transplated to Argenteuil in 1960. Her wish was denied, however, and she was buried in the royal crypt alongside King Leopold and his first wife, Queen Astrid. Queen Fabiola and Lilian's step-children attended the funeral, as did Lilian's son Alexandre and her daughter Marie-Esmeralda. Lilian's long estranged daughter Marie-Christine, however, did not attend. Following Princess Lilian's death, a cardiological conference was organized and prominent doctors and surgeons such as DeBakey and many others rendered a fervent homage to Lilian, her extraordinary personality, and her contributions to cardiology.