Yuri Gagarin gained worldwide fame as the first man in space. But the unsung hero of the Soviet Union's triumph was a brilliant scientist called Sergei Korolev. Korolev remained in the shadows throughout his career and was only revealed to have masterminded the USSR's rocket wizardry after his death in 1966.  Guest: Stephen Walker, author of Beyond: The Astonishing Story of The First Human to Leave Our Planet and Journey into Space (published by Harper Collins)