Complex sentence: McCann was in a relationship with Arthur Collins from 2016, whom she planned to marry, however they split up in April 2017 after he was arrested for an acid attack which took place in a London nightclub.
Split into simpler sentences: McCann was in a relationship with Arthur Collins from 2016, whom she planned to marry. However, they split up in April 2017 after he was arrested for an acid attack which took place in a London nightclub.