He was parliamentary editor of De Maasbode [nl], and fled to England during World War II where he served for the Dutch government-in-exile.

He served as Governor of Curaçao and Dependencies from 15 July 1942 until 4 August 1948, Dutch Ambassador to Chile (1948–1956), to Ireland (1956–1966) and briefly to Israel (1966).

[6] In 1938, he received his doctorate in political and social sciences from KU Leuven on a biography of prime minister Abraham Kuyper.

[3][7] On 14 May 1940, after the German invasion of the Netherlands, Kasteel as a known anti-fascist boarded a fishing boat leaving his wife and children behind, and arrived in England two days later.

[1] After retiring, Kasteel moved to Via della Conciliazione in Rome, Italy near the Vatican where his son Karel [nl] served in the Apostolic Camera.