English breakfast tea is a traditional blend of teas from Assam, Ceylon and Kenya. It is one of the most popular blended teas and the most common form of British tea culture.
English breakfast tea is a black tea blend usually described as full-bodied, robust, and/or rich, and blended to go well with milk and sugar, in a style traditionally associated with a hearty English breakfast.
Drinking a blend of black teas for breakfast is indeed a longstanding British custom. The practice of referring to such a blend as "English breakfast tea" appears to have originated not in England but America, as far back as Colonial times.