So the first part is:

there is a massive archive

hidden in a working salt mine in the north of England.

And the second part is: it's not just for documents.

Because there's so much space available,

it's also an archive for actual physical objects, for "stuff".

Now it's very rare that someone who is not

an employee or an archive client is allowed down here,

particularly to make a video.

Because there are public records, important government archives,

and a lot of things that I'm not allowed to go near,

let alone film.

Confidentiality is important,

and someone is looking over my camera op's shoulder

to check where that lens is pointing.

We are 150 metres underground

and about a kilometre into that mine...

is DeepStore.

Ready when you are!

- The area that the mine occupies is around 3.5km east to west,

and about 2.5km north to south.

And at the moment we're about 1.5km away from the mining activities.

We use what's called a "room and pillar" mining technique.

We don't just extract great big massive voids of salt.

There are massive pillars of salt,

of which I'm actually stood next to one now,

which make the mine so stable and support the roof.

So where DeepStore comes in is:

we actually build inbetween these pillars,

and in-between these pillars is what we call

the repositories, or the rooms.

And then we plane the floors, they're painted,

we install the racking, we install the air conditioning.

Originally, the mining started around about 1850

and it really got going around the turn of the century, 1900.

Since then, it's simply grown and grown and grown

up to the present day where now we're extracting

around a million tonnes each year.

DeepStore was set up in the 1990s

because we've got the perfect atmosphere

down here to store items.

The salt creates a naturally occurring dry atmosphere.

And of course with the racking,

nothing naturally comes into contact with the salt.

Because this is relatively a shallow mine,

we're around 150 metres, 400-500 feet,

and because of the salt bed,

it has created this natural ambient temperature of 14-15°

along with a relative humidity of 53-55%,

which anybody in the archive and storage world knows,

naturally occurring, that is absolutely fantastic.

What we've been able to do is actually enhance these conditions

and modify them even more to client requirements.

So by the use of air conditioning and air filtration,

we can make the atmosphere in here to really whatever a client requires.

The atmosphere in these storage rooms

is actually clearer than it is on the surface.

- It's almost impossible to get across

the sheer scale of the mine and the archive on camera.

And out there, where it's still a working mine,

I can taste salt in the air, there's clouds of it that lands on you.

But in here, things are a little bit more controlled.

It is public knowledge

that somewhere in the many, many vaults here,

there are files from the British National Archives

and core samples drilled out for soil tests

during the construction of Crossrail.

Other than that, well, DeepStore aren't saying.

More through wanting to be cautious about

revealing details of their clients,

rather than any strict secrecy.

But the folks who actually got in touch and invited me here

have a very different reason

for storing actual physical things long-term.

- Laura Ashley is a UK interiors lifestyle and fashion brand.

Within the cabinets in this room, there are hand drawn artworks,

some of them hundreds of years old

that have been developed into wallpapers or fabrics.

But we also have fabrics, dresses, rolls of wallpaper,

metres of the fabric that we've produced over the years stored in the archive.

It's a continually growing archive for Laura Ashley.

It's really important for us to archive the original physical pieces.

So we can really understand,

it's those techniques of how they were made.

If you scanned that, if you created a digital archive,

you would lose that history to that piece.

When you can touch and feel

and see some of these amazing antique documents,

you can really see the brushstrokes in the artwork

or how they were printed initially.

And it might be that we actually want to recreate

how they were printed, not just how they look.

- We can't keep everything.

It would be nice if entropy didn't exist,

but until humanity fixes that,

preservation and archiving will take skill, time, and money.

And the more you preserve, the more upkeep it takes.

Perhaps the most important decision any archivist has to make

is what to keep and what to throw away.

- So we've got almost a hundred thousand items

in this Laura Ashley archive,

but that is by no means everything that was ever manufactured.

We will always keep masters

so wallpaper and fabric is core to what Laura Ashley is.

Original artworks would never be thrown away.

The Laura Ashley pieces

in this archive date back to the really early period.

So people may donate pieces to the Laura Ashley archive,

that could be a Laura Ashley bowl

that you used to have in your house in the 1980s

or your mum's wedding dress from the 1970s.

It's fantastic for us to be able to see

that we're following in the footsteps of the people who came before us.

- We've got over three and a half million

of items under storage, be it a box or be it an artefact.

We have more than 40 rooms

of the same standard or even better standard

than what I'm actually standing in now.

This is probably one of the largest single repositories in the country.

Currently, we occupy 14 to 15%

of the actual mined void area underground,

which means we've got amazing amounts of space to expand into.

I mean, really, if you were to convert this entire site,

eventually you'd probably be able to store

just about every single archive box in Europe.