Invasion! Brian Cox and Robin Ince are joined by comedian Phill Jupitus, bat expert and ecologist Professor Kate Jones and forensic botanist Dr Mark Spencer to look at the problems caused by alien invasions, although not of the little green men kind. They look at why such innocent and innocuous sounding plants such as floating pennywort strike terror and fear in the heart of environmentalists up and down the country, and how clever microbes and diseases are able to jump from animals such as bats to humans causing devastating consequences. Producer: Alexandra Feachem.