The Union Jack flag combines the crosses of England, Wales, Scotland (Northern Ireland joined the union in 1921). This was combined with the previous Union Flag of St George and St Andrew, after the Act of Union of Ireland with England (and Wales) and Scotland on 1 January 1801.

The flag consists of three heraldic crosses:

1) The cross of St George, a red cross on a white ground.

2)  The cross saltire St Andrew, patron saint of Scotland, is a diagonal white cross on a blue ground.

3) The cross of St Patrick, patron saint of Ireland, is a diagonal red cross on a white ground.

The Union Jack Flag is one of the most recognisable flags to be flown across the United Kingdom of Great Britain, Northern Ireland and the rest of the world.