Sam's father Peter Woodhead thanked all the people who found his son: "We have just had so much support from friends and family. I would like to put on air the thanks we give to everyone who joined in their search effort. He owes his life to them."
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A "public-spirited" passerby retrieved the child.
A man wanted in connection with a hit-and-run crash which killed a four-year-old girl has been arrested, police have confirmed.
Scotland's First Minister was pictured with her feet up on the sofa while penning the document to Theresa May.