Before you listen to this BBC podcast I'd like to quickly tell you about some others.

My name's Andy Martin and I'm the editor of a team of podcast producers at the BBC in Northern Ireland.

It's a job I really love because we get to tell the stories that really matter

to people here, but which also resonate and apply to listeners around the world.

And because the team is such a diverse range of skills and strengths. We have trained journalists, people who love digging through archives, we've got drama and even comedy experts. We really can do those stories justice.

So if you like this podcast, head to BBC Sounds where you'll find

plenty more fascinating stories from all around the UK. Hello you're listening to the Witness History podcast from the BBC World Service

with me Matt Pintus. Whether you love it hate, think it's art or vandalism, you'll spot graffiti all over the world.

And in recent years, street artists like Banks, you have been able to make millions from their work.

But that wasn't always the case.

This month marks 40 years since the release of a book

that put street art firmly on the map,

a book that became known as the Bible of graffiti.

This is the story of the world.

Two of the city's leading urban photographers have decided to meet up.

They've got a plan.

Each of us were trying to do a book separately and I think we were feeling pretty

competitive at that time who was going to get the first book and then when we

tried to get publishers for our idea, we failed, singularly, we failed.

Miserably.

And then decided maybe we should pool our resources.

That's Henry Schaufont and Martha Cooper.

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