Complex sentence: The Richmond Park by-election is an expected UK parliamentary by-election in the Westminster constituency of Richmond Park triggered by the resignation of the Conservative Member of Parliament Zac Goldsmith on 25 October 2016 over the Government's proposal for a third runway at Heathrow Airport.
Split into simpler sentences: The Richmond Park by-election is an expected UK parliamentary by-election in the Westminster constituency of Richmond Park triggered by the resignation of the Conservative Member of Parliament Zac Goldsmith on 25 October 2016. He resigned over the Government's proposal for a third runway at Heathrow Airport.