Which event did Spencer Perceval's assassination directly impact?

Spencer Perceval was assassinated in 1812, making him the only British Prime Minister to have been murdered while in office. His assassination had a significant impact on parliamentary security measures in the UK. Following his death, there was a heightened awareness of the risks associated with political leadership and the vulnerability of public officials. This incident prompted reforms and the implementation of new security protocols aimed at protecting members of Parliament, as well as addressing broader concerns over the safety of politicians and the functioning of government.

The other events listed do not directly relate to the consequences of Perceval's assassination. World War I occurred many years later and was influenced by different factors, while British political parties were already forming and evolving in ways that were not solely affected by this particular event. The American Revolution was largely concerned with the American colonies' struggle for independence from Britain, which was unrelated to Perceval's assassination and its implications for UK domestic politics.