Cassian was born in 1962, the sixth of ten children. Educated at Ampleforth College and Henley Business Management College (Graduating with an MBA 2002), he was commissioned into the Irish Guards in 1982, serving in West Germany BAOR, Northern Ireland, London, Afghanistan with HALO trust in 1989, Berlin 1990, Oman, Egypt, Kosovo and Sierra Leone. He was promoted Lieutenant Colonel on the Counter Terrorism Training Team in 1996 (Egypt) before retiring in 2000.