Union Jack
The Union Jack flag could falter should Scotland vote yes to leave the UK  Reuters

Scotland's independence referendum has posed questions about the legitimacy of the Union Jack, after a flag expert revealed that the UK is one of the few nations not to have a binding legislation over its official flag.

Charles Ashburner, CEO of the Flag Institute, a charity that documents flags, told Reuters: "This situation is terribly British in that we are almost unique among developed nations in muddling through. Virtually every other country has this sorted out, with legislation for the flag and its use, and this needs to change for the UK if Scotland votes for or against independence."

In short, the UK has yet to adopt the Union Jack as its official flag. If the situation arises in which Scotland's electorate votes for independence, there is some confusion as to what would happen to the flag, since none of the constituents of the UK have full authority over it.

The flag is a combination of the individual flags of England, Scotland and Northern Ireland and there's no place for the Welsh dragon in its design.

Its current design harks back to 1801, when Ireland joined the union, adding the diagonal red cross of the St Patrick flag to the original design, which dates from 1606.

In 2008, the Union Flag Bill sponsored by Conservative MP Andrew Rosindell, was introduced in Parliament. The bill sought to remove legal obstacles to the flag's regular display and to officially recognise the name 'Union Jack' as having equal status with 'Union Flag'.

The bill failed to reach the second reading stage, meaning the UK is hurtling towards the most defining moment of its 200-year plus existence with the future of its flag mired in ambiguity.

If Scotland leaves the union, it would ostensibly have no reason to fly the flag. However, what would happen in England, Northern Ireland and Wales is unclear.