Watch the report from Richard Morgan below:
A father from Cardiff who spent four years trying to get the truth about his seven-year-old son's death says he fears lessons haven't been learnt despite the publication of a report into failings at the Bristol Children's Hospital.
Luke Jenkins had been expected to make a full recovery from heart surgery but died of complications.
The report examined 11 deaths involving children at the hospital.
More top news
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).