Watch: How experts stumbled upon a priceless document in a university library

A manuscript - once considered an unofficial copy of Magna Carta - is now believed to be a genuine version and ''one of the world's most valuable documents'', according to UK academics.

Harvard Law School paid $27.50 (then about £7) for it in 1946 and for years it has remained tucked away in its library, its true identity unknown.

But two medieval history professors have concluded it is an extraordinarily rare and lost original Magna Carta from 1300 - and could be worth millions.

BBC Newsbeat's Eleanor Doyle explains.

Video by Tom Joyner, Anna Lamche, Ian Casey and Tom Richardson.