Prince Frederick Adolf, Duke of Östergötland

He was given the title Duke of Östergötland on 8 September 1772 and the Tullgarn Palace as his residence.

During the great succession scandal, the so-called Munck Affair in 1778, when the queen dowager Louisa Ulrika questioned the legitimacy of the Crown prince in reference to the rumors that Gustav III had convinced Adolf Fredrik Munck to impregnate the queen, Sophia Magdalena of Denmark, Frederick sided with his mother and defended her before the king by pointing out that these rumors had not been invented by their mother but were in fact widespread rumors, and he reportedly said to his brother the king: "The entire city is talking of it, and it is commonly believed that You are not altogether man, and that it is because of this reason, that You have enticed the Queen to it to have an heir to the Kingdom."[2] It was Frederick who convinced Louisa Ulrika to receive Gustav III on her deathbed in 1782, thereby accomplishing peace between them.[1]

His sister-in-law, Hedwig Elizabeth Charlotte of Holstein-Gottorp, describes him as beautiful, with expressive eyes, an easygoing temper, and very handsome when he dresses properly, though often badly dressed in his private life, and gives the estimation that he would have been a greater social success, if he did not say so many suggestive things and had such a filthy mouth [that is to say, he used a sexually suggestive language], which he acquired because he had spent too much time with men, and had such a weakness for women and sex. He had no tasks in his life other than the ceremonial, and spent his life wasting money and involving himself in love affairs. Gustav III reportedly had no high opinion of his intellectual capacity.[1] Frederick was an honorary member of the Swedish Royal Academy of Fine Arts, and he did occasionally show a genuine interest in the affairs of the academy, as well as in the management of the Västmanland regiment.[1] He devoted much time to country life on his estate, Tullgarn. His economic affairs were in bad shape, and in 1791 he was finally declared bankrupt and placed under administration until 1802.[1]

Frederick served in the Russo-Swedish War in Finland in 1788. During the Battle of Hogland, Fredrick wished to send reinforcements by fleet to aid his brother, Duke Charles. This was prevented, and Frederick left the army in protest to Gustav III, whom he referred to as a tyrant.[1] He thereby came to belong to the opposition, and he also became involved in the planned coup by his sister-in-law to depose the monarch; the 1789 Conspiracy. In the autumn of 1789, Hedvig Elisabeth Charlotte prepared to depose Gustav III and place her husband Duke Charles upon the throne.[3] Her ideal was the Swedish Constitution of 1772, which she saw as a good tool for an enlightened aristocracy, and the war and the Union and Security Act had made her a leading part of the opposition. She cooperated with Prince Frederick Adolf and Gustaf Adolf Reuterholm.[3] The plan was to force Charles to act as a symbol of the opposition to the Union and Security Act when the time was right.[3] When the time arrived to make Charles act, however, he refused, which effectively discontinued the coup.[3]

In July 1793, he was given the position to chair the government during the journey of the king and the regent in the southern provinces, but nothing whatsoever was apparently accomplished during his tenure, and during a similar journey in 1794, he was not entrusted again.[4]

In 1800, Frederick Adolf left Sweden for health reasons and travelled to Germany and then to France. He died in Montpellier in France in 1803.

Prince Fredrick Adolf is in fact most known in history for his love life. He was never married, and the ceremonial duties of his consort were performed by his sister Sophia Albertina. He had several plans to marry, but none of them was realised. His first proposal was to the Countess Ulla von Höpken, but she was married to another, and he accompanied his brother Gustav to France in 1770 to forget her. In 1774, he proposed to the cousin of his former love, Countess Sophie von Fersen, daughter of Axel von Fersen the Elder and sister of Axel von Fersen the Younger, the alleged lover of Marie Antoinette. She and her father refused, as they were afraid that she would be badly treated by his brother and mother, who was reluctant to give their consent, and because she was already engaged, and Frederick Adolf was sent to Italy in 1776 until she was married.[5] He lived from 1778 to 1795, in a happy relationship with the ballet dancer Sophie Hagman, who was well liked at court, and had a daughter, Sophia Frederica, with her. In 1780, he temporarily ended his relationship with Hagman and proposed to the noble Margaretha Lovisa Wrangel, with whom he became informally engaged. The King gave his permission to the marriage with the condition that it was postponed for a year, during which Wrangel was sent to Scania, with the thought that his brother would change his mind when the time was up. This was also the case, and Frederick Adolf returned to Hagman in 1781.[6] After his relationship with Hagman ended, he proposed to Princess Augusta Sophia of the United Kingdom in 1797, and after his relationship with Euphrosyne Löf ended, he proposed to Dorothea von Medem, dowager duchess of Courland in 1801, but none of the marriages was realized.[6]