Dr George Findlay, Cardiff and Vale University Health Board's Clinical Board Director for Children and Women, told ITV News that between six and 12 inches of water had flooded the top two floors of the Children's Hospital for Wales - and some ceiling tiles had come down with the force of the water.
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Investigating officers say a driver's intentions were "genuine" when he offered a mother and child a lift during a downpour.
The Wales squad have been put through their paces ahead of tomorrow's Six Nations clash against Scotland in Cardiff.
John McDonagh, 41, was jailed for four years for what a judge described as a despicable offence.