Arwel Jones from the National Library of Wales told ITV News that he is hoping that the damage will be limited - "the most valuable stuff is housed in purpose-built cells at the very bottom of the library, and this fire is at the very top."
He admitted to concern that the damage from water pumped onto the building by firefighters would be as bad as the fire damage.
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The Met Office has issued a yellow 'be aware' warning of rain for parts of south Wales with a risk of localised flooding.
Showers overnight will make way for heavy rain tomorrow! The Met Office has issued a warning to be aware!
Dermatology services in west Wales are at breaking point say top skin experts in Wales. Hywel Dda currently has no consultant dermatologist.