Overview:Michael Portillo continues his journey north on Robert Stephenson's first inter-city railway line from the capital. Along the line at Bletchley he meets one of the Second World War's most secret agents, discovers a poet in Olney whose words are still sung today and explores the first purpose-built railway town at Wolverton. Michael's last stop on this leg is Newport Pagnell, where he learns the ancient craft of vellum making.