Complex sentence: Sam Tom followed Ramsay MacDonald when the Labour Party split in 1931, defending the seat successfully in 1931 and 1935 for the National Labour Party, being succeeded in 1939 by Commander Stephen King-Hall for National Labour.
Split into simpler sentences: Sam Tom followed Ramsay MacDonald when the Labour Party split in 1931, and then defended the seat successfully for the National Labour Party in both 1931 and 1935. He was succeeded in 1939 by Commander Stephen King-Hall for National Labour.