Irish Breakfast is strong and robust and high in caffeine with a usually blend of 3 black teas from India, Ceylon & China. A higher Assam content gives this a higher caffeine level but also more astringent than an English Breakfast. On the East Coast it is sometimes just an Assam blend.
Irish Breakfast black tea became the stronger version of the English Breakfast blend. Tea was introduced to Ireland by the English aristocracy at the beginning of the 19th Century. The initial Irish to drink this were the wealthy but later, as in England, it was drunk by the working class, but not in the same circumstances. Instead of drinking in the afternoon with High Tea parties it was drunk with breakfast and dinner to help supplement the food. Started with workers drinking tea at their work break instead of beer and Landowners realized that the work output was much higher and provided free tea.
The blend is very strong and can take plenty of milk and sugar without losing its tea taste. The English and Irish compete with who drinks the most per capita – around 5lbs per year which is around 700 cups per year.
The English have always made jokes about the Irish and vice versa, and say that the Irish need more caffeine to be able to get to work in the morning.
Check out the other breakfast teas.