The UK Justice Secretary, Chris Grayling, says the prison which will be built in north Wales will be 'Britain's biggest'.
He says the announcement is a very important part of upgrading Britain's prisons.
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Showers in the north will spread southeastwards overnight. Temperatures will be higher so not as chilly as list night.
Chilly start to Tuesday, turning into a largely fine and dry day.
Political Editor Adrian Masters was joined in the studio by assembly members Bethan Jenkins, Mick Antoniw and Suzy Davies.