Union Jack: 400 years old

Four-hundred years old this week, the union jack is one of the world's oldest national flags... if you overlook the fact it's only meant to be flown at sea, the proportions are wrong and no one can agree on its name.

Its striking red, white and blue design harks back to a time when Britannia ruled the waves, but the history of the union jack is as tangled as all the mothballed bunting it decorates.

It is a story about custom over clarity, assumption over assertion, anomaly instead of consistency.

The union jack as we know it today dates back to 1801, when Ireland joined Great Britain in a single kingdom. But the original flag, which was set out by royal proclamation on 12 April 1606, was subtly different, lacking the diagonal red lines - the so-called St Patrick's cross.

The flag was the result of the union of the English and Scottish monarchies in 1603, under James I (as he was in England) or James VI (as he was in Scotland).