Wednesday, 7.30pm, History Channel Remember Broken Arrow, with John Travolta striving to secure a stolen nuke? This broken arrow (Pentagon code for a lost warhead) isn’t it: in fact it is much scarier. In 1950 engine failure takes a US bomber down on the west coast of Canada, but while most of the crew are rescued the bomb isn’t. A modern expedition sets out to discover whether the weapon was armed or not. If it was, where is the plutonium core and why wouldn’t the Pentagon talk then or now? Suspicious stuff, especially given the US sent a team in to blow up the downed aircraft in 1954. But perhaps not suspicious enough to sustain a whole documentary, so this one includes a history of early Cold War weapons, notably the enormous B36 bomber and its armaments. The documentary team finds the wreck and looks for evidence that the bomb was armed, which they don’t find. For a supposedly secret mission a great deal of information is available, making this an insight into the Cold War — the bomber’s mission was to simulate a Soviet attack on San Francisco. But it’s way short of identifying a conspiracy.