Doubt has been cast over one of the longest-standing economic claims in the Brexit debate after a Sky investigation revealed that Britain's real exports to outside the EU are actually far lower than official figures suggest.

The Government's trade statistics show that, over the past five years, the share of UK goods being exported to the European Union was only 46% - a fact frequently referred to by those who campaigned for Brexit.

However, this number is severely distorted by the flow of gold bullion in and out of London - the world's major centre for the trade of this precious metal.

When gold is excluded from the trade figures, the numbers are transformed - with half of UK physical exports over the past five years going to the EU.

Image: Britain's trade figures are transformed once gold is excluded

It underlines the fact that once one adjusts for these volatile financial flows, Europe remains a crucial export destination for UK goods - significantly more so than the overall numbers suggest.


:: Long read: Gold takes the shine off Britain's trade balance

The Sky News analysis of Britain's trade with the rest of the world underlines just how much these figures have been distorted by movements of gold - almost all of which is produced in other countries and is simply passing through London's financial markets.

How gold distorts Britain's trade figures

In July alone, the latest month for which trade figures exist, gold accounted for more than a tenth of the value of everything exported by the UK overseas - making it Britain's top export above cars, engines and pharmaceuticals.

Since the vast majority of this gold is shipped to non-EU countries such as China, Switzerland and India, the upshot of these gold figures is to swell the total amount of goods reported as being shipped outside Europe.

Officials from the Office for National Statistics say they are aware of the distortions and are taking action to adjust for it, recently publishing some of their trade figures excluding gold and other erratic components.

However, they have not adjusted the geographical breakdown of trade accordingly.

Image: The Queen visits the Bank of England's gold vaults in 2012

The scale of the distortions caused by the flow of gold are such that they also have an impact on the national accounts.

In the fourth quarter of last year, a sharp outflow of gold showed up as a sudden spike in exports, causing some economists to conclude that Britain's manufacturers were starting to benefit from a post-Brexit jump in confidence.

In fact, the spike was primarily a sign of investors pulling gold out of vaults in London.

:: Beneath the sound and the fury of the Brexit negotiations, what's actually going on? Brexit Forensics is a series of stories from our specialist correspondents, revealing the issues and the themes behind the headlines that will really determine the course of the Brexit revolution.