If you’re a European Economic Area (EEA) national, you don’t need a visa to visit (or work in) England or any other part of the UK. Citizens of Australia, Canada, New Zealand, South Africa and the USA are given leave to enter the UK at their point of arrival for up to six months (three months for some nationalities), but are prohibited from working.
UK immigration authorities are tough, and if they suspect you’re here for more than a holiday, you may need to prove that you have funds to support yourself, details of any hotels or local tours booked, or personal letters from people you’ll be visiting. Having a return ticket helps.
Visa and entry regulations are always subject to change, so it’s vital to check before leaving home. Your first stop should be www.ukvisas.gov.uk or www.ukba.homeoffice.gov.uk, and if you still have queries contact your local British embassy, high commission or consulate.