Complex sentence: Duquesne was one of many Boer prisoners sent to Bermuda, where he was one of an estimated 360 prisoners interned on Burt's Island, the second smallest of the then-five self-governed internment islands.
Split into simpler sentences: Duquesne was one of many Boer prisoners sent to Bermuda. He was one of an estimated 360 prisoners interned on Burt's Island, the second smallest of the then-five self-governed internment islands.