Time travel is well known for creating paradoxes. Chief among them is the famous "insanity paradox", whereby a completely barking mad TV programme attracts rave reviews from critics. All the laws of physics and popular culture say that this shouldn't be possible and yet the evidence is there for everyone to see.
The script writers for the BBC serial Life on Mars clearly live on another planet if they think viewers are following all the barmy twists and turns in their plot lines. If you didn't see it this week, I'm afraid it's hard going, so you might want to skip the next para.
Our favourite sleeping policeman, Sam Tyler, feels compelled to nick a bloke he knows will go on to commit mass murder in years to come. So far, so Minority Report. But Sam can't bang this bloke up by the book. He therefore resorts to the same dodgy methods that were previously the preserve of his nemesis, DCI Gene Hunt. When these techniques don't work either, Sam's left with only one option. He gets the would-be murderer to state publicly that he's been arrested by a crackpot, time-travelling policeman. The future crim's story seems so absurd that he's promptly taken away by the men in white coats.
I've given up thinking there might be an interesting ending to this show. Even all the seventies stuff - the period glue that holds this dodgy pack of cards together - is looking increasingly contrived. The love-interest WPC is now name-checking Wagon Wheels in the canteen. Way too obvious, darling. Be a love and go and fetch us another cup of tea now, will you?