The beauty queen, the Mormon missionary tied to a bed – Joyce McKinney's bizarre story gripped Britain in the 1970s and is now retold in a fine documentaryJoyce McKinney is one of those names that for people of a certain age opens a doorway into the past. To mention it is to be transported back to the 1970s, when there were only three TV channels, British food was awful, sex was naughty and Fleet Street was still the home of national newspapers.