Question: Who was the prime minister under which the predecessor of Derick Heathcoat Amory served?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/property/successor> <http://dbpedia.org/resource/Derick_Heathcoat-Amory,_1st_Viscount_Amory> . ?x <http://dbpedia.org/property/primeminister> ?uri  . }