Otto von Habsburg, the oldest son of Austria-Hungary’s last emperor who saw the end of his family’s centuries-long rule and emerged to become a champion of a Europe united by democracy died aged 98.

Archduke Habsburg died in his sleep at his home in Poecking in southern Germany, where he had lived since the 1950s, with his seven children nearby, his spokesperson said.

Archduke Habsburg used his influence in a vain struggle to keep the Nazis from annexing Austria before the Second World War, then campaigned against the Soviet empire in the decades after the war.

With the fall of the Berlin Wall, he used his seat in the European Parliament to lobby for expanding the EU to include former Eastern bloc nations.

“My father was a towering personality,” Archduke Habsburg’s oldest son Karl Habsburg-Lothringen said. “With him we lose a great European who has influenced everything we do today beyond measure.”

Born in 1912 in Austria, Archduke Habsburg witnessed the family’s decline after the empire was dismantled and Austria became a republic following the First World War.

He became head of the family at his father’s death in 1922 and continued to claim the throne until the 1960s.

He was a member of the European Parliament for the conservative Bavarian Christian Social Union in southern Germany and also served as president of the Pan-European League from 1979 to 1999.