Introduction and fundamental themes

Esso Petroleum v Customs & Excise [1976] 1 WLR 1
http://www.bailii.org/uk/cases/UKHL/1975/4.html

Chappell & Co Ltd v Nestlé Co Ltd [1960] AC 87
http://www.bailii.org/uk/cases/UKHL/1959/1.html