1. The cross of St George, patron saint of England since the 1270's, is a red cross on a white ground.
2. Because it combines the crosses of the three countries united under one Sovereign - the kingdoms of England and Wales, of Scotland and of Ireland.
3. The cross of St Andrew, patron saint of Scotland, is a diagonal white cross on a blue ground.
4. The cross of St Patrick, patron saint of Ireland, is a diagonal red cross on a white ground.
