How do you dig a 26 mile tunnel beneath a city and below the water table? This week we drop in on Crossrail, who are busy constructing a new commuter line below the UK capital, to discover how massive tunnels are made in the modern era. Plus, we take a walk along the World's first and oldest tunnel built below a river to hear how it was made, and we find out what present-day tunnelling is turning up of London's past. Also, news of a drug that can repair the brain damage done by multiple sclerosis, and a planet found floating alone in interstellar space...