John Craven celebrates the beauty of the Malvern Hills, while Keeley Donovan is in Scotland to investigate how the New Zealand flatworm, an invasive species, is destroying the earthworm population. Keeley gets the lowdown on how to keep them at bay. Paul Martin joins in a spring-clean on a stretch of canal in Birmingham. He discovers how Dhruv Boruah and his extraordinary bike boat are causing quite a splash. Horrified at the haul of rubbish retrieved from the water and the canal side, Paul discovers what harm litter is doing to wildlife and potentially to humans. Margherita Taylor is at Secret World Wildlife Rescue Centre in north Somerset for the first of three special Countryfile Spring Diaries reports. Jules Hudson is at 17th-century Worsbrough Mill in South Yorkshire, where the miller is retiring and the search is on to find a replacement. Matt Baker is out at sea as he joins the RNLI for a high-octane training exercise.