Salisbury Cathedral is home to one of four surviving copies of the historic document, the Magna Carta. Issued by King John in 1215 as a solution to a political crisis he was facing.
It established for the first time the monarch was subject to the law of the land, rather than above it.
Although nearly a third of the text was dropped or substantially rewritten within ten years and almost all the clauses have been repealed in modern times, Magna Carta remains a cornerstone of the British Constitution and its principles are echoed in the US constitution and others around the world.
As well as providing a once-in-a-lifetime opportunity for researchers to study the documents together, the unification will be a chance for 1,215 members of the public to see the manuscripts side-by-side after winning free tickets in an public ballot.
More top news
Amanda has the Bank Holiday forecast for the west of the Meridian region.
Amanda Houston has the Bank Holiday weekend forecast for the east of the Meridian region.
The family and girlfriend of one of the Shoreham air disaster victims, Jacob Schilt, have spoken about their terrible loss.