Complex sentence: St. Conleth's initially opened on the day Germany declared war on Poland, interestingly the sons of both the Polish and German ambassadors to Ireland attended St. Conleth's together on that day.
Split into simpler sentences: St. Conleth's initially opened on the day Germany declared war on Poland. Interestingly, the sons of both the Polish and German ambassadors to Ireland attended St. Conleth's together on that day.