The National Archives has one of the largest conservation departments in the UK. It employs 30 people - 7 in the Book Conservation section, 13 in the Manuscripts section, 3 in the Maps section and 4 in the Seals & Exhibitions section. Most of the conservators will have a degree in paper conservation or bookbinding or equivalent experience.

The department employs people who already have some experience, but they also run an in-house development program of three to three and a half years. Below you can read interviews with Angela, who heads up the book conservation section and John, who works in the manuscript area.

Angela, what is your job?

I'm in charge of the book conservation section in the conservation department.

How do you decide what to conserve?

All the items we conserve fall into at least one of three categories - they must either be high use, be unfit to be handled or have intrinsic value. In practice this means that we might be working on a project to rebind a large set of documents that have been identified as high use - such as the Admiralty Ships' Musters (series ADM 36); making new boxes for our most valuable items kept in our strong room; or working on a document that is unfit for production that has been suggested by a reader.

How do you decide how to rebind or repair a book?

First of all we assess whether the binding can be repaired or if it has to be replaced. We also decide whether to faithfully reproduce the look and construction method of an original binding. Our aim in conserving the books is to preserve the text within them and to make sure that they can stand up to being handled by the public for hundreds of years to come. Therefore materials are chosen for their technical properties such as strength and flexibility. We also try to construct the bindings so that they can be removed in the future without damaging the paper/text within.

Can you show us an example of an old and new binding?

On the left is a Commission book from the series WO25 (War Office records) which dates back to 1740. It is bound in reversed calf.

The new binding shown on the right, uses cotton buckram for economy and its ability to be folded back and forth frequently without damage.

However cotton has bad abrasion resistance so pigskin "overbands" have been sewn on with vellum to counter this.

We have replicated the attractive stitch pattern used in the original.

What are you working on at the moment?

One of the bindings I am working on is from the series E405 and this particular book records the "First Fruits and Tenths" - the tithes paid to a newly appointed priest.

It qualifies for conservation in that it is from a class of high use and intrinsic value. The binding is crumpled and split but has an unusual sewing structure so it would be wrong to replace it. The paper sections are sewn onto leather supports (straps) and then onto alum tawed (a specially treated leather) supports. We have quite a few examples of this - the outer bindings are different, but the paper is sewn onto leather. A colleague of mine suggested that perhaps the books were sold like that - half-bound, so that the individual could choose the outer binding.

In order to preserve the original binding and to make the document suitable for handling by the public, I am going to encase the vellum in an inert polyester cover.

I will carefully and discreetly re-sew some of the paper sections where the original sewing is damaged incorporating new alum tawed supports. The new supports will then be threaded through the polyester cover.

What is the most interesting document you have ever handled?

Well, I have to admit that it wasn't one held by The National Archives - it was Shakespeare's First Folio and it was at the Folger Shakespeare Library in the United States.

And have you done your own research here at the National Archives?

Yes, I did a masters degree on the 'History of the Book' so I did a lot of research here looking at Lanthony Priory books, and at Lambeth Palace.