Complex sentence: Independently, Chesterton had also been discussing the issue of a unification with Bean's BNP, which proved more successful, with the LEL and BNP merging to form the National Front (NF) in 1967.
Split into simpler sentences: Independently, Chesterton had also been discussing the issue of a unification with Bean's BNP. This proved more successful, for the LEL and BNP merged to form the National Front (NF) in 1967.