UK National Flag.

The flag of the United Kingdom, called the Union Flag or Union Jack is a combination of the crosses of the patron saints of United Kingdom.

The red cross on a white background of the center is St George of England. The white saltire on a blue backround is the cross of St. Andrew of Scotland.

And the red salitre on a white backround is the cross of St.Patrick of Ireland.

Its name comes from 1707 when the Royal Navy adopted the design for their boats, which was informally renamed Union Jack.