This is The Guardian.

Hi, I'm Nicola Davis, a science correspondent here at The Guardian, and this is the final

episode of a special Science Weekly mini-series.

A Scottish Tea Mystery.

Episode 3, a bag for life.

If you missed episodes one and two, it's best to go back and listen to them first.

You'll want to hear the whole story.

When Food Standard Scotland investigator Stuart Wilson had collected all the information he could

on Tamo Bran and his supposedly Scottish teas, the evidence pointed one way.

Neither the tea plants nor the vast majority of those finished products were genuine.

The plants had arrived in Scotland from the sunny shores of Lake Maggiore in Italy,

and Professor David Burslem had explored the origins of the processed teas, confirming most clearly did not come from Scottish soils.

And so Stuart set about finding out where they had come from.

We applied for warrants for his bank account and within that we identified two wholesalers of tea. So one wholesaler from

Oxford area, another wholesaler from London area. So we went and visited them. We identified that

over the period of roughly 2015 to 2019, he'd bought many hundreds of kilos of various tea types

from both of these wholesalers.

And I suppose ultimately when we balanced them all together,

the quantities were almost similar to what he'd sold to the hotels.

There was one particular tea type I remember called silver needles,

and that's a really expensive tea type. And we knew that 13 kilos

of silver needles had been sold to the Balmoral Hotel. And we were able to identify that in the

...