Robbie Cumming concludes his journey by travelling from Barton Swing Aqueduct to Liverpool Docks - but he experiences engine issues and a leaky boat along the way

Fred visits the North East, a region rich in transport history, to explore the development of Britain's railways, from the first steam locomotives to the record-breaking Mallard. A visit to York's National Railway Museum offers the chance to ride a replica of Stephenson's Rocket, while at Ffestiniog Railway he learns about the computer-aided design process used for new locomotives

Part two of two. Following the challenges involved with building the Hinkley Point C in the remote Somerset countryside, the first new nuclear power station in Britain for a generation. This time, the team creates an extensive flood defence system to protect the site from a nuclear disaster like the one that befell the Fukushima Daiichi power plant in Japan. Elsewhere, cameras follow specialists as they work to uncover unexploded Second World War bombs that threaten the installation of the 4500-tonne cooling water intake heads

Gabriel Weston explores the forensic advances that have elevated murder weapons from mere instruments to crucial pieces of evidence. She sees how arsenic, the undetectable weapon of choice in the 19th century, was exposed as the killer thanks to one simple chemical test, and finds out how distinctive marks on a victim's skull led to the weapon and, in turn, the killer. Gabriel also looks at the latest forensic developments, from 3-D laser scanning that can reconstruct the sequence of events at the scene of a gun crime to the pioneering chemistry able to determine where in the world someone has been based on just a few strands of their hair