A British Library has raised £1.1 million to buy an early biblical manuscript, which scholars believe holds the key to discovering more about the development of the New Testament.

The Codex Zacynthius has been housed by the Cambridge University Library since 1984. It was, however, owned by the Bible Society, which decided to sell the manuscript to raise funds for a visitor centre in north Wales.

Supported by Dr Rowan Williams, former Archbishop of Canterbury, the Cambridge University Library launched a campaign to secure funds, and now hopes to study the New Testament manuscript in greater detail.

According to the Associated Press, the document features "an early seventh century script which has been partially scraped away and written over to make way for a 13th century entry."

Re-using manuscripts was common practice at the time, and the undertext was deciphered in 1861. However, it is thought to include errors which could now be rectified.

Williams said: "The discovery and identification of the undertext represents a fascinating detective story. By securing the manuscript, we hope that multispectral imaging techniques will enable scholars to recover fully the hidden text."

Executive director of charity at the Bible Society, Paul Woolley, added: "As Lord Williams so rightly said, the thrilling aspect of this sale both for Cambridge and ourselves is that scholars now have the opportunity to use techniques, such as multi-spectral imaging, to uncover the hidden text that were previously unavailable to them.

"As custodians, not technical experts, Bible Society has never been in a position to uncover the hidden gems in the manuscript in the same way. So the excitement today among many academics who will finally be able to solve this great detective story is overwhelming."

Woolley also enthused about the new Welsh visitor centre to celebrate Mary Jones – who at 15 years old in 1800, walked 25 miles to purchase a Bible from Rev Thomas Charles. Her determination encouraged Charles to found Bible Society several years later.

The centre will be based at St Beuno's Church at Llanycil, Bala, where Rev Thomas is buried.

"Mary Jones World will not only tell the story of Mary Jones, Thomas Charles and the world's bestselling book, but will show the impact of the Bible on Wales and the world," Woolley said.