Bluebirds keeper David Marshall says the side's first Premier League game at home this afternoon is a big occasion for fans and players alike.
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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).