Complex sentence: De Kempenaer was appointed to the Constitution Commission headed by Johan Rudolph Thorbecke in 1848, and as Minister of the Interior and "de facto" Prime Minister he played an important role in the creation of the revision of the national Constitution.
Split into simpler sentences: De Kempenaer was appointed to the Constitution Commission headed by Johan Rudolph Thorbecke in 1848, and as Minister of the Interior. He soon became "de facto" Prime Minister, playing an important role in the revision of the national Constitution.