The flag of Great Britain, known as “Union Jack” or “union flag”, is a combination of emblems of three countries controlled by one monarch. These emblems are the crosses of the three patron saints:

red on a white field cross of St. George, the patron saint of England

white diagonal on a blue field cross of St. Andrew – a symbol of Scotland

red diagonal cross of St. Patrick, patron saint of Ireland.

The modern design of the flag appeared in 1801, when Ireland became part of the Kingdom of Great Britain. However, the very first flag, established by royal decree of April 12, 1606, was slightly different: it did not have diagonal red lines – the St. Patrick’s Cross. This cross is still present on the national flag of Great Britain, despite the fact that nowadays only northern Ireland is part of it.