Grand Duke Jean is the world's oldest monarch and was succeeded by his son, Henri, both shown here. Cour Grand-Ducale / Lola Velasco / Archives

Grand Duke Jean is the world's oldest monarch and was succeeded by his son, Henri, both shown here. Cour Grand-Ducale / Lola Velasco / Archives

The 98-year-old monarch had been hospitalised over the weekend due to a lung infection. He remains in hospital under observation for the time being.

Grand Duke Jean, who turned 98 in January, is the world’s oldest living monarch and served as Grand Duke from 12 November 1964 to 7 October 2000. He was succeeded by his son, Henri.