Today - 05/07/2008

Presented by John Humphrys and Edward Stourton. Including: Demand is growing for an international ban on organ trafficking and what has been called transplant tourism. With Dr Adrian McNeil, the chief executive of the Human Tissue Authority. It is 20 years since the Piper Alpha rig in the North Sea caught fire, resulting in 167 deaths. Journalist Stephen McGinty recalls the rescue effort in a new book called Fire in the Night. He and Michael Jennings, who was one of the survivors, remember the tragedy. Knife crime in London has overtaken terrorism as the Metropolitan police's top priority. Rod Morgan, chairman of the youth justice board for England and Wales, looks at the strategy for tackling the problem. Charles Darwin may have seriously considered the possibility that life arrived here in a meteorite. Dr John Van Whye, a historian of science at Cambridge, has been exploring this theory for a paper he is giving. He discusses the possibility with Dr Caroline Smith, meteorite curator at the Natural History Museum. Boris Johnson has been mayor of London for two months, but already two of his senior appointees have been forced to resign. Prof Tony Travers from the LSE considers the implications. Video evidence has emerged of the vote-rigging which appears to have taken place during the presidential election in Zimbabwe last month.