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The BBC has released a new teaser trailer for The Split<\/a> ahead of the legal drama\u2019s return for its third and final run on BBC iPlayer next month.<\/p>\n The brief 35-second clip sees Nicola Walker and Stephen Mangan reprise their roles as Hannah Defoe and Nathan Stern respectively, as their once-perfect marriage crumbles around them and their divorce proceedings turn sour.<\/p>\n \u201cHe wasn\u2019t supposed to fall for someone else,\u201d Hannah says at the start of the trailer before her mother Ruth (Deborah Findlay) asks: \u201cWhy can\u2019t they ever just stick with meaningless sex?\u201d<\/p> We later hear Nathan\u2019s lawyer outline: \u201cMy client wishes to spend one night a week in the family home,\u201d before we see Hannah confront new character Kate, played by Sherlock star Lara Pulver.<\/p>\n \u201cTread carefully,\u201d she tells her, with Kate responding: \u201cIs that a threat?\u201d<\/p>\n Meanwhile, Nathan informs Hannah: \u201cYou no longer have a say over what I do\u201d \u2013 in one of many bad-tempered exchanges between the pair.<\/p>\n The clip ends with Hannah revealing that Christie Carmichael \u2013 her ex-boyfriend who acted as something of a catalyst in their divorce \u2013 is in town before we see the pair sharing a passionate kiss. You can watch the teaser in full below.<\/p>\n \u201cTread carefully\u2026\u201d