lies an important landmark in this country's history.

I'm Rob Bell, engineer and adventurer and I'm exploring some of the most fascinating

and significant sites in England's industrial heritage.

Grimes Graves is a complex of Neolithic flint mines.

It first operated over four and a half thousand years ago and continued for several hundred years

In the present day, visitors are still able to descend an open shaft

and walk in the footsteps of those prehistoric miners.

Before we head down, let's meet with English Heritage historian Susan Greaney

to find out more about this prehistoric site

- Hello - Hi

- Susan, nice to meet you - Welcome to Grimes Graves

Thank you very much. It's quite a landscape!

- I'm not sure as I've seen anything like it before really - It's amazing, isn't it? It's a really special place

And all these divots and bunkers all around - they're the actual flint mines, are they?

Yes, each of these hollows is the top of one of the really deep shafts that goes down

- There's about 430 of them here at Grimes Graves - Wow

This is the only place in the country where you can actually go down into a Neolithic flint mine

- And we can do that right here, right now? - We can do that

I was hoping you'd say that

Susan, it's great to be down underground here.

What exactly is Grimes Graves and where does its name come from?

Well Grimes Graves comes from the Anglo Saxons

who gave this funny undulating landscape the name of Grim, who was their god - also known as Woden.

So it's 'grimes' and then 'graves' - as in pits or hollows

How important was flint in Neolithic Britain?

What kind of things was it being used for?

Flint was the most important material for Neolithic people

It was used to make every single tool that you can imagine

It's kind of the Swiss Army knife of the Neolithic.

To make make axes, to make knives, to make cutting tools, boring tools

Anything really where you needed a cutting edge

Well, what was being used before flint was discovered and started being used for all these tools then?

Flint was in use for a really, really long period of time

So right back into the Paleolithic period - the Ice Age here in Britain

Before that they were using stones to pound and break things

but not really working stone in such a way

Mining is a hard, hard graft

I'm now thinking about the tools and machinery that they might have had

available to them and I'm guessing it's rudimentary, if anything really?

The main tool that they were using was antler picks.

So they were using these both to hammer out the flint

and also to chip away at the chalk to expose areas of flint.

Flint is quite a strange material in some ways

It's incredibly hard, but most of it appears in kind of nodules

So you're just taking out nodules from the ground that are already self-contained

and if you strike flint in the right place, it breaks in a very predictable way

so people would have been able to break up pieces quite regularly

It's phenomenal to think that this hole we're stood in now was dug out by antlers

Was this just another flint mine amongst a number of flint mines around Britain?

The flint here in this part of Norfolk is particularly high-quality.

I've got a little bit here to show you. You can see it's this beautiful black colour

It's got no impurities in it - it's really pure.

It seems that people were deliberately selecting this type of flint, because it was very easy to work

and created amazingly good and sharp, and hard tools

So they were probably coming here deliberately.

The reason they were digging down so deep, was here it occurs as something called floor stone

which is a complete layer of this very black, pure flint. So it's quite unique

Once they'd established that it was here on this site, all shafts they'd go down for that third layer?

They'd drop down their shafts to that layer and then go out sideways into little galleries and passages

- And that's what we're seeing around us here? - Yep, that's what you're seeing here

And then they're just following the line of that floor stone and digging it out

In a shaft like this, that would be open to the skies

But when you go off into these galleries I imagine it's got to get pretty dark in there?

Yeah, the shafts themselves would stay relatively open to the daylight so that's okay

But once you're off down the galleries it's very dark.

We have found very small little chalk lamps in some of these mines

and some of them have been found to have traces of oil in them.

So it's quite likely they were taking in little lamps or perhaps burning tapers of some kind

The people would have been mining this flint which is incredibly sharp

They probably would have had cut hands a lot of the time

But they'd also have been white - they'd have been covered in chalk dust

So for people coming down here mining this flint would've been quite an experience

And you'd have known which people have been down mining because they would have looked so different.

Once the flint's been dug out from the ground then, what happens to it?

So once it gets up to the top of the shaft

they're working it into what we call 'rough outs', which are the basic rough shape of an axe

Just knocking off all the sides of the nodule that you don't want to be carrying around with you

And then those rough outs are exported

Do we know where these products might have gone on to?

We know that it gets transported all across southern England.

There's even a hint that perhaps that it gets across to the continent, into France

Because it's such good quality and because it's this lovely dark colour

it can be made into the most beautiful polished axes and things

people do seem to have been transporting it a very long way from its origin here

Do you think that those people who were involved in the mining here

would have known the significance and the quality of the flint that they were mining?

Or was it just another flint mine for them?

They knew. They knew that this was particularly special and important flint

They came back here and dug over 430 shafts over many hundreds of years

They would have been famous. People across southern England would have known -

Grimes Graves - that's where the really black flint comes from

What happened for there to be an end to the mining of the flint here at Grimes Graves?

Grimes Graves is being dug in the very end of the Neolithic period, the end of the Stone Age

And what happens is that basically metal arrives from the continent.

And of course bronze as a material is very very hard -

it's much more efficient at doing things like cutting down trees

and it's also mouldable - you can make it into any shape you wish

So really, metal takes over as the tool of choice

and here at Grimes Graves, flint mining stops

Susan, thank you so much for bringing me down here. It is fascinating to come and learn exactly what's gone on here

It's been a pleasure

When you come to Grimes Graves, the first thing you notice is this bizarre landscape

These pitted craters all around you - and that's intriguing enough

But it's even more fascinating when you get to scratch beneath the surface

and find out just how important an operation this flint mine was to prehistoric progress in this country

Grimes Graves is open to the public during the warmer months of the year

and you can find out everything you need to know to plan your visit on the English Heritage website

And whether you're more interested in what's above-ground, or beneath the ground

I can tell you, it's well worth the trip.