Secret of lunar split: what occurred actually in 1178?

In June, 1178 group of monks of Canterbury, England, became witnesses of the unusual phenomenon in the sky. They saw how the Moon, according to them, broke up in two. This event intrigued decades modern astronomers and historians, and all of us still open new helps and theories that could cause this mysterious lunar phenomenon. The event was recorded by the monk Gervas Kenterberiysky in the manuscript under the name Gesta Stephani. Gervais wrote down as about 9 o'clock in the evening that night the moon became more and more, and then monks saw how "the top horn of the moon broke up in two...