But despite dating back to the 14th century, diners still can't agree on the best items on a Full English Breakfast. While many enjoy the meaty elements, others argue that a Full English just isn't complete without a healthy serving of grilled mushrooms. To settle the debate once and for all this Full English Breakfast Day, MailOnline has enlisted the help of ChatGPT. So, do you agree with the AI bot's rankings? But despite dating back to the 14th century, diners still can't agree on the best items on a Full English Breakfast Today is Full English Breakfast Day, which is celebrated by millions of people internationally, according to the English Breakfast Society.