Ed's note: The complete series of The Written World is available to download as a podcast until Monday morning, after that you will still be able to listen online but the downloads won't be available - PM.

The 7th century St Cuthbert Gospel - the earliest intact European book

In a nondescript seminar room in the British Library, Melvyn Bragg and I sit waiting at a conference table. We are there to interview the library's Lead Curator of Medieval and Earlier Manuscripts, Claire Breay, who after greeting us has disappeared into the bowels of the building to retrieve a prop.

After a few minutes she reappears, carrying a small wooden box. It doesn't look much, but it contains an object so precious that it's kept in a strongroom, and only one person - Claire - is allowed to handle it.

She slides off the lid to reveal a small linen-wrapped package. There is an undeniable tension in the room as she removes this protective covering to reveal a small leather-bound volume.

This is the St Cuthbert Gospel, the oldest surviving European book, produced in Northumbria in the 7th century; it owes its immaculate condition to the fact that it spent the first four hundred years of its existence in the saint's coffin.

A great privilege, to see such treasure at close quarters. But over the course of a few weeks in November while recording In Our Time: The Written World, Melvyn and I had several of these memorable encounters.

In the atmospheric library of Durham Cathedral, Richard Gameson showed us a detail in a medieval Gospel and casually let slip that we were looking at the oldest illuminated manuscript in the Western world. In Cambridge, Simon Schaffer showed us one of Newton's most celebrated experiments, described (and drawn) in the scientist's own hand.

And then there was the never-to-be-repeated day in the British Library, when in the space of a few hours we were shown a dizzying array of priceless objects: the world's oldest printed book (not European but Chinese, produced in 868); the only surviving manuscript of Beowulf; and not one but two Gutenberg Bibles.

When Melvyn and I first came up with the idea for this series early last year, our intention was to investigate how the inherent qualities of writing have shaped intellectual history. We wanted the focus to be artefacts: tablets, manuscripts and books, all of which in some way represented a turning point in the history of ideas.

Choosing the right ones was quite a challenge: five programmes, it turns out, is not much airtime to tell such a vast and complex story. So we asked some of the academics who regularly appear on In Our Time for advice. Their recommendations, and those of the institutions we visited, made up an almost bewildering list of goodies - ruthlessly and reluctantly pruned back to a more manageable fifteen or so.

Having a wishlist of precious objects is one thing; getting to see them quite another. But we were treated with great indulgence by all the institutions we approached: the British Library gave us wonderful access to some of the greatest things in their collection; Cambridge University Library filled a meeting room with Korans, history scrolls and - wonder of wonders - Newton's student notebooks; and in Durham we saw one of the earliest copies of Bede's Ecclesiastical History.

If I have one regret, it's that we left so much untouched.

We squeezed in all we could, but it would have been nice to have had time to discuss Jewish scriptures, Islamic science, the birth and spread of the novel, the impact of writing on politics... the list goes on.

Perhaps one day we'll have an opportunity to fill some of these gaps. And no doubt we missed all sorts of unmissable documents, turning points in the history of the written word that should have been included - if so, please feel free to let us know!

Tom Morris is producer of In Our Time

• The Written World is only available to download as a podcast until Monday but after that you will still be able to listen online.
• BBC News slideshow: The books that shaped history
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