It was a murder plot all captured on CCTV: the victim, and the disguised hit squad who stalked then killed him in a hotel room in Dubai. But who murdered senior Hamas military commander Mahmoud al-Mabhouh, and why? Panorama's Jane Corbin tracks down the answers in Israel, Gaza and Dubai, and shows how British passports and stolen identities were used in a crime which was never meant to be revealed to the world.