Matt Baker and Helen Skelton head for the Oxfordshire countryside. Matt's taking a walk on the wild side in search of its wild beasts including the humble hedgehog. Matt discovers what's being done to halt the decline in the hedgehog population which has halved in the last 25 years. While Helen's at the home of croquet - Chastleton House and gardens where she'll be getting to grips with the rules for a match against the estate volunteers. There will also be the judging of Countryfile's annual photographic competition. Every year Countryfile's talented viewers send in tens of thousands of entries to the programme's photographic competition. This year is no exception - around 50,000 photos will be scrutinised to find the final twelve that will feature in the Countryfile calendar for 2013. Last year, the calendar raised more than one-and-a-quarter million pounds for Children in Need, so there's a lot of pressure on the judges to get it right. As usual, former competition winners will help shortlist the entries before John Craven, naturalist and photographer Chris Packham and writer comedian Jo Brand find the final twelve. Then it's up to the viewers to vote for the overall winner. Elsewhere, Tom Heap investigates the impact of rising sea temperatures on our marine life.