The Health Minister, Mark Drakeford AM, says despite an increase in the numbers of people who don't smoke in cars when children are present there is still a stubborn percentage of people who still do. He says he wants to close that gap and introducing the law will make the final difference.
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It'll be a dry and fine end to the day, with a dry night then following.
The world bog snorkelling championships returns to Llanwrtyd Wells this weekend.
A cloudy start with a scattering of showers spreading eastwards, allowing some warm sunshine to develop from the west during the afternoon.