Complex sentence: Vivian MacKerrell was a British actor of the 1960s, who shared a house with film director Bruce Robinson, director of "Withnail & I", and was reputedly the major basis for Withnail's character, a memorable character of British cinema.
Split into simpler sentences: Vivian MacKerrell was a British actor of the 1960s, who shared a house with film director Bruce Robinson, director of "Withnail & I". He was reputedly the major basis for Withnail's character, a memorable character of British cinema.