Countryfile - Heatwave Special: As the heat bakes the British countryside into crisis, Adam Henson and John Craven meet those on the front line. They include the farmer who is double sewing and trying a new crop; the wildlife champions battling to save chalk streams - some of the most vital but fragile habitats in the world; and the firefighters and scientists contending with the wildfires ravaging swathes of our landscape.