Before the arrival of digital TV, access to subtitles on UK TV could be turned on by starting ceefax/teletext and pressing 888 on your remote control. If the program was subtitled the text would appear for the broadcasted programme you were watching. I stumbled across a blog that celebrates some of the mistakes made by live subtitling from 888. Like the subtitles themselves the examples are helpfully colour-coded as follows:
Green = Live subtitling mistake
Yellow = TV audio
Blue = Broadcast information (The TV show/broadcast during which the error occurred.)
Check out the blog here. It also has some interesting links including one for history fans that looks at the early testing of some of the first ceefax/teletext subtitles in the UK.