Complex sentence: After Asquith's fall in December 1916, Simon remained in opposition as an Asquithian Liberal until he lost his seat at Walthamstow, at the "Coupon Election" in 1918.
Split into simpler sentences: After Asquith's fall in December 1916, Simon remained in opposition as an Asquithian Liberal. Simon lost his seat at Walthamstow, at the "Coupon Election" in 1918.