On Track in Greensand Country: a journey by rail on the Marston Vale Line. Terry Lee and Lawrie Hallett are taking the 45 minute journey by rail on the Marston Vale Line, from Bedford to Bletchley. We’ll be alighting at some of the stations too, learning about some of the local greensand landscape, history and characters along the way. Greensand Country is a beautiful and loved landscape. It is defined by the Greensand Ridge, a band of higher ground stretching from Leighton Buzzard to Gamlingay, which rises out of the surrounding vales to create a locally unique environment.