The aim and purpose of the thesis is to examine and set out the case for a modernised impeachment process for the United Kingdom. The thesis identifies and considers the arguments for a new impeachment process to operate within, and buttress, existing forms of political accountability at Westminster. It considers the counter-arguments and issues and problems involved. It will argue that the authority of the UK Parliament has been weakened in recent years and that impeachment could perform a valuable part in strengthening its role, functions, and power within the country's unwritten constitution. The thesis examines the present law and history on impeachment in the United Kingdom, which today is widely regarded as having fallen into desuetude and its procedures inappropriate for modern conditions. It will examine how impeachment operates in two countries, the United States and Denmark, selected respectively for their marked differences and similarities to the United Kingdom's political and constitutional system, for the purposes of illumination and possible lessons for a new impeachment process for the United Kingdom. The subject is one of topicality and considerable public interest by reason of some recent high-profile political controversies, such as the two impeachments of President Trump in the US, and calls for former Prime Minister Tony Blair to be impeached in the United Kingdom for his alleged misconduct over the military invasion of Iraq. This thesis provides a balanced and independent examination of the case for a new impeachment process for the United Kingdom, concluding that it would have a valuable role to play in the future development of the United Kingdom's system of politics and government. It concludes by setting out a detailed model for the structure, working, and effect of impeachment.