Complex sentence: UKIP began as the Anti-Federalist League, a Eurosceptic political party established in 1991 by the historian Alan Sked which opposed the Maastricht Treaty, which had been recently signed, and sought to sway the governing Conservative Party toward removing the United Kingdom from the European Union.
Split into simpler sentences: UKIP began as the Anti-Federalist League, a Eurosceptic political party established in 1991 by the historian Alan Sked. The League opposed the recently signed Maastricht Treaty and sought to sway the governing Conservative Party toward removing the United Kingdom from the European Union.