Complex sentence: Giles Fearnley and Stuart Wilde set up Blazefield in 1991 when they purchaed 70% of Alan Stephenson's AJS Group, which owned West Yorkshire Road Car and London Country North East.
Split into simpler sentences: Giles Fearnley and Stuart Wilde established Blazefield in 1991 when they purchaed 70% of Alan Stephenson's AJS Group. AJS had owned West Yorkshire Road Car and London Country North East.