Of course, the original John Simm ‘is he dead/mad/in-a-coma’ drama was fairly bonkers in the first place, but when former Spooks star Keeley Hawes tumbled into Sam Tyler’s delusion and found everything looking exactly the same – played by the same actors, and everything – something didn’t quite click.

Certainly, in real terms, it was because Philip Glenister was always in danger of stealing the show, and having another man play the sheriff would have, in audience terms, been a big mistake. But in respect of story and logic, this always meant that something else had to be going on – was the delusion real? Is the past, indeed, just another country? And, crucially, was Sam Tyler still around for a cameo?

You shouldn’t ever really write for the fans, but these really are important issues, so it’s pleasing to report that there are hints that these issues will be, if not resolved, then at least spoken about in a mysterious and frustrating way, not least by new character Jim Keats (played by Daniel Mays), who has a deposition for DCI Gene Hunt, and a frustrating hint of exposition for Alex Drake, all the while coming across like the bullied science kid in a Woody Allen film.

Kicking off Series 3, it’s now impossible to tell where Drake’s Twilight Zone is. Back in our present day, she’s started having dreams of the team back from the ’80s, which might suggest that she hasn’t even come back from being shot by her boss (as he tells her, ‘you weren’t that shot’). Adding to the confusion is the slight vagueness around the edges of Drake’s ’80s experiences – slyly, a kidnap victim is a little girl in a gingham dress called Dorothy (continuing a string of references to The Wizard Of Oz that began way back in the first series of Life On Mars).

Drake may not be back from the future and she might even be originally from the ’80s. All is confusion and darkly muttered hints for now, leaving the main body of the episode to be police procedural drama, the kind that they really don’t make any more, and while there’s a suggestion that the show keeps the one on one dynamic that the two lead characters had in Life On Mars (‘You’ve got a chemistry’, Keats tells them), this is much more of an ensemble piece, with supporting characters essential.

Sharp-eyed viewers will note that not every scene has Alex Drake in it, suggesting that everything may not be in her imagination. Will there be life after Mars, or will it be all dust to dust? Time, indeed, will tell…

Airs at 9pm on Friday 2nd April 2010 on BBC One.