Khat is banned around the world, but not in the UK. Now there are fears this herbal stimulant could cause lasting damage to a community in Wales.
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There will be a fresher feel with temperatures falling lower than on recent nights.
The accident between junction 24, Coldra, and 23A, Magor, has closed the eastbound carriageway.
Eloise Parry, 21, died after taking diet pills containing the poisonous Dinitrophenol (DNP).