In fact, this piece...
It is brought on to the beach by the tide. If you are north of the mouth of the River Tyne it probably comes from coal seams exposed on the seabed. If you are south of the Tyne then it is more likely to be the debris from the many coal mines along the cliff tops in the old days.
One of the researchers for the TV show tracked down some evidence on my blog and we met the producer to show him where to find sea coal and places where he could film easily. On filming day he chose the southern beach with Redcar steel works in the background.
After all that it was fish and chips at "The Almighty Cod" as a just reward.
We were mentioned in the acknowledgements at the end as well.
If you missed it it should be on i-player for a while or something like that. It was a great show and worth watching.