Complex sentence: He led the EDL from 2009 until 8 October 2013, when he left to discuss reforms with the "counter-extremism" think tank, Quilliam.
Split into simpler sentences: He led the EDL from 2009 until he left the group in October 2013. On 8 October 2013, Tommy Robinson quit the EDL to discuss reforms with "counter-extremism" think tank, Quilliam.