Why the mighty Stonehenge was built around 5,000 years ago has long been one of the great mysteries.  

But according to a new study, we may finally have an answer. 

Scientists say Wiltshire's famous stone circle was built as a symbol of unification between three distinct corners of Britain.  

We know that Stonehenge's rocky slabs were transported as far afield from southwest Wales and northeast Scotland. 

So the scientists, from University College London and Aberystwyth University, theorise that Scottish and Welsh people brought their own local stones down to Wiltshire as a well-meaning contribution to assembling the structure.

In that sense, it represented a powerful – and very early – symbol of British unity. 

Stonehenge's builders had attempted to establish 'political unification and shared identity across much or even all of Britain', the authors say in their paper, published in Archaeology International.  

They add: 'Bringing together these extraordinary and alien rocks... symbolised and embodied far and distant communities within a complex material.

'[Stonehenge was a] monumental expression of unity between people, land, ancestors and the heavens.' 

In the paper, the researchers say Stonehenge's long-distance links add weight to the theory that the Neolithic monument may have had some unifying purpose in ancient Britain, to go with its symbolic value. 

'The fact that all of its stones originated from distant regions, making it unique among over 900 stone circles in Britain, suggests that the stone circle may have had a political as well as a religious purpose,' said lead author Professor Mike Parker Pearson at UCL's Institute of Archaeology. 

'[It was] a monument of unification for the peoples of Britain, celebrating their eternal links with their ancestors and the cosmos.' 

Even though England, Scotland and Wales did not exist as concepts when Stonehenge was built 5,000-odd years ago, we know the structure is indeed representative of all three countries.