Depends on whether one is talking of national or international politics.

On a national level, Nye Bevan has to be considered as the architect of both the National Health Service and our social welfare programme.

It could also be argued that either Oliver Cromwell or John Pym who wrested the reins of power away from the autocratic Charles 1 and established our present parliamentary democracy.

On the International scene Thomas Paine - whose 'The Rights of Man' formed the basis of both the American and post revolutionary French Constitutions. It is also the basis of the European Convention on Human Rights and our own Human Rights Act.

Vladimir Illich Ulyanov might also be considered as changing the course of history, and similarly Josef Djugashvili.

Adolph Hitler and Benito Mussolini would also fall into the same category too.

Further back in history Alexander the Great and Genghis Khan would also be candidates.