Complex sentence: Gardiner left provincial politics the next year to join the federal cabinet of Liberal Prime Minister William Lyon Mackenzie King as Minister of Agriculture holding that portfolio for twenty-two years until 1957 when the Liberal government was defeated.
Split into simpler sentences: Gardiner left provincial politics the next year to join the federal cabinet of Liberal Prime Minister William Lyon Mackenzie King as Minister of Agriculture. He held that portfolio for twenty-two years until the 1957 federal election when the Liberal government was defeated.