On 29 October 1950, Crown Prince Gustaf Adolf became king at age 67 upon the death of his father, King Gustaf V. He was at the time the world's oldest Crown Prince. His personal motto was Plikten framför allt, "Duty before all". During Gustaf VI Adolf's reign, work was underway on a new Instrument of Government – eventually taking effect in 1975 after the king's death – to replace the 1809 constitution and produce reforms consistent with the times. Among the reforms sought by some Swedes was the replacement of the monarchy or at least some moderation of the old constitution's provision that "The King alone shall govern the realm." Gustaf VI Adolf's personal qualities made him popular among the Swedish people and, in turn, this popularity led to strong public opinion in favour of the retention of the monarchy. Gustaf VI Adolf's expertise and interest in a wide range of fields (architecture and botany being but two) made him respected, as did his informal and modest nature and his purposeful avoidance of pomp. The monarchy was, however, made subordinate to a democratic state. Additional powers of the monarch were removed when Sweden's constitutional reform became complete in 1975. The King died in 1973, ten weeks shy of his 91st birthday, at Helsingborg Hospital after a deterioration in his health that culminated in pneumonia. He was succeeded on the throne by his 27-year-old grandson Carl XVI Gustaf, son of the late Prince Gustaf Adolf. In a break with tradition, he was not buried in Riddarholmskyrkan in Stockholm, but in the Royal Burial Grounds in Haga alongside his two deceased wives.