Monaco's Prince Rainier, Europe's longest-reigning monarch, has died at the age of 81, after spending several weeks in hospital. He had been suffering from heart, kidney and lung problems. He will be succeeded by his 47-year-old son, Prince Albert, who took over his father's royal duties last week. A palace statement said Rainier died from the "broncho-pulmonary, heart and kidney conditions that caused his hospitalisation". Rainier III made world headlines with his marriage to Hollywood movie star Grace Kelly in 1956 after meeting her at the Cannes film festival.