Complex sentence: During Speed's intitial stint in the show her character's main storyline centred around her affair with Bianca's boyfriend Ricky Butcher (Sid Owen), which culminated in Natalie's departure from the serial in February 1995.
Split into simpler sentences: During Speed's intitial stint in the show her character's storylines centred her affair with Bianca's boyfriend Ricky Butcher (Sid Owen). The climax of the storyline led to Natalie's departure from the serial in February 1995.