You may be familiar with the Union Jack flag of the United Kingdom, but you may not be familiar with how it got that way. It is made up of the Northern Ireland diagonal red cross of St. Patrick and the Scottish flag of St Andrew which is a diagonal white cross on a blue background, all combined with this flag of St George. Notably there is no symbol for Wales which is the other of the four combined nations as by the time of the "Union", Wales was already joined with England.
This shot was taken in Birmingham where a large Victorian hotel was being refurbished. I suspect this was not an official display but put up by one of the workmen behind the covers. There was probably a football tournament on at the time as this flag usually appears during football season where the four nations compete separately.
The country's official name is The United Kingdom of Great Britain and Northern Ireland. In this case "Great" is used in the geographic sense as the largest island of the British Isles. A lot of people think we call the country "Great" because we are just so big headed but it in fact it is just to describe the main island that contains most of England, Scotland and Wales. I would not risk telling the people of Ireland though that they live on "Lesser" Britain.