Complex sentence: The Regimental Mascot was the Cheetah: originally there were two particular cheetah cubs who served as mascots, but following their ill-fated deaths on 6 October 1963 the role became applied to the animal in general.
Split into simpler sentences: The Regimental Mascot was the Cheetah: originally there were two particular cheetah cubs who served as mascots. Unfortunately, following their ill-fated deaths on 6 October 1963, the role became applied to the animal in general.