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This is In Our Time from BBC Radio 4,
and this is one of more than a thousand episodes you can find in the In Our Time archive.
A reading list for this edition can be found in the episode description wherever you're listening.
I hope you enjoy the programme.
I've chosen Plate Tectonics for the latest of our summer selection from Melvin Bragg's
In Our Time because I was listening to the programme live when it first went out almost
20 years ago and it literally stopped me in my tracks.
I was heading out the door in a rush but became so fascinated by the discussion
I cancelled my meeting in order to finish listening to Melvin and his guests.